Method and system for monitoring oxygenation levels of a compartment for detecting conditions of a compartment syndrome

ABSTRACT

A method and system for continually monitoring oxygenation levels in real-time in compartments of an animal limb, such as in a human leg or a human thigh or a forearm, can be used to assist in the diagnosis of a compartment syndrome. The method and system can include one or more near infrared compartment sensors in which each sensor can be provided with a compartment alignment mechanism and a central scan depth marker so that each sensor may be precisely positioned over a compartment of a living organism. The method and system can include a device for displaying oxygenation levels corresponding to respective compartment sensors that are measuring oxygenation levels of a compartment of interest. The method and system can also monitor the relationship between blood pressure and oxygenation levels and activate alarms based on predetermined conditions relating to the oxygenation levels or blood pressure or both.

REFERENCE TO RELATED APPLICATIONS

The present application claims priority to provisional patentapplication entitled, “Near Infrared Compartment Syndrome (NICS)Monitor,” filed on Feb. 27, 2007 and assigned U.S. Application Ser. No.60/903,632. The entire contents of the provisional patent applicationmentioned above is hereby incorporated by reference.

FIELD OF INVENTION

The invention relates to a coordinated, continual and real-time methodand system for monitoring oxygenation levels of a compartment in orderto detect conditions that are likely caused by a compartment syndrome.More particularly, the invention relates to an orchestrated method andsystem that monitors oxygenation levels and that is provided withsensors having markers so that the sensors can be precisely positionedover a compartment of interest in order to assist with a compartmentsyndrome diagnosis.

BACKGROUND OF THE INVENTION

Compartment syndrome is a medical condition where the pressure inside acompartment, which is a muscle group surrounded by fascia or a thin,inelastic film, increases until the blood circulation inside the volumedefined by the fascia or thin film is cut off. The most common site, inhumans, occurs in the lower leg, and more specifically, in regionsadjacent to the tibia and fibula. There are four compartments in thelower, human leg: the anterior (front), lateral (side next to thefibula) and the deep and superficial posterior (back).

These four compartments surround the tibia and fibula. Anyone of thesefour compartments can yield a compartment syndrome when bleeding orswelling occurs within the compartment. Compartment syndrome usuallyoccurs after some trauma or injury to the tissues, such as muscles orbones or vessel (or all three), contained within the compartment.Bleeding or swelling within a compartment can cause an increase inpressure within that compartment. The fascia does not expand, so aspressure rises, the tissue and vessels begin to be compressed within thecompartment.

This compression of tissue, such as muscle, due to intra-compartmentalpressure can restrict and often times stop blood flow from entering thecompartment that is destined for any tissues contained within thecompartment. This condition is termed ischemia. Without blood flow totissues, such as muscle, the tissues will eventually die. This conditionis termed necrosis.

A simple working definition for a compartment syndrome is an increasedpressure within a closed space which reduces the capillary bloodperfusion below a level necessary for tissue viability. As noted above,this situation may be produced by two conditions. The first conditioncan include an increase in volume within a closed space, and the secondcondition is a decrease in size of the space.

An increase in volume occurs in a clinical setting of hemorrhage, postischemic swelling, re-perfusion, and arterial-venous fistula. A decreasein size results from a cast that is too tight, constrictive dressings,pneumatic anti-shock garments, and closure of fascial defects. As thepressure increases in tissue, it exceeds the low intramusculararteriolar pressure causing decreased blood in the capillary anastomosisand subsequent shunting of blood flow from the compartment.

The clinical conditions that may be associated with compartment syndromeinclude the management of fractures, soft tissue injuries, arterialinjuries, drug overdoses, limb compression situations, burns,post-ischemic swelling, constrictive dressings, aggressive fluidresuscitation and tight casts.

Referring now to the Figures, FIG. 1 illustrates an X-ray view of ahuman leg 100 with fractured bones of the tibia 105 and fibula 110 thatlead to one or more compartment syndromes in the muscles 115 surroundingthe bones of the human leg 100. The tibia 105 and fibula 110 usuallybleed in regions proximate to the physical break regions 120. Thisbleeding can form a large pool of stagnant blood referred to as ahematoma. The hematoma can start pressing upon muscles 115 that may beproximate to the break 120. This pressure caused by the hematoma canseverely restrict or stop blood flow into the muscles 115 of acompartment, which is the diagnosis of a compartment syndrome.

Traditional Methods for Diagnosing Compartment Syndromes

Referring now to FIG. 2, this Figure is a side view of a human leg 100in which compartment pressures are being measured with a large boreneedle 200, having a gauge size such as 14 or 16 (which is the largestneedle in the hospital available to clinicians), according to aconventional method known in the prior art. While compartment pressurescan be measured with this conventional method, the method is highlyinvasive procedure which can cause tremendous pain to the patient.Needles with large gauge sizes of 14 or 16 are analogous to sticking apatient with an object as large as a nail or a pen.

In addition to causing tremendous pain to the patient, there are severalmore problems associated with the conventional needle measuring method.First, it is very challenging for a medical practitioner to actuallymeasure or read pressure of a compartment since the needle must bepositioned at least within the interior of a compartment. To enter theinterior of a compartment, the needle 200 must penetrate through severallayers of skin and muscle. And it is very difficult for the medicalpractitioner to know if the needle has penetrated adequately through theintermediate layers to enter into the compartment. This challengesignificantly increases if the patient being measured is obese and hassignificant amounts of subcutaneous fat in which to penetrate with theneedle.

Often, the medical practitioner may not have a needle accuratelypositioned inside a compartment which can yield a reading of the tissueadjacent to the compartment, such as muscle or skin. Such a reading ofmuscle or skin instead of the compartment of interest can provide themedical practitioner with elevated or depressed pressure readings thatdo not reflect the actual pressure contained within the compartment ofinterest. Pressure readings inside a compartment have been shown to vary(increase) based on the depth of the reading as well as the proximity tothe fracture site.

Because of the challenge medical practitioners face with preciselypositioning a needle within a compartment of interest and because of thenumerous law suits associated with the diagnosis of compartmentsyndrome, many medical schools do not provide any formal training formedical practitioners to learn how to properly place a needle within acompartment of interest for reading a compartment's pressure. Therefore,many medical practitioners are not equipped with the skills orexperience to accurately measure compartment pressures with the needlemeasuring method.

Currently, intra-compartmental pressures are the only objectivediagnostic tool. Due to the legal climate regarding this condition,clinicians are forced to treat an elevated value for compartmentpressures or expose themselves to legal ramifications with anycomplications. As described later, the treatment of compartment syndromecan cause significant morbidity and increase the risk for infection.Therefore inaccurate and elevated pressure readings are a very difficultand potential dangerous pitfall.

Another problem associated with the training and experience required forthe needle measuring method is that, as noted above, compartmentsyndromes usually occur when tissues within the compartment areexperiencing unusual levels of swelling and pressure. With this swellingand pressure, the tissues do not have their normal size. Therefore, anytraining of a medical practitioner must be made with a patient sufferingunder these conditions. A normal patient without any swelling would notprovide a medical practitioner with the skills to accurately assess asize of a compartment when using the needle measuring method fordetermining compartment pressure. Put another way, due to the traumaassociated with the injury, normal anatomy is not always present whenattempting to measure compartment pressures.

In addition to the problem of entering a compartment that may have anabnormal size or anatomy, the needle measuring method has the problem ofproviding only a snap-shot of data at an instant of time. When theconventional needle measuring method is used, it provides the medicalpractitioner with pressure data for a single instant of time. In otherwords, the needle pressure method only provides the medical practitionerwith one data point for a particular time. Once pressure is read by themedical practitioner, he or she usually removes the needle from thepatient. The data obtained from a single measurement in time gives noinformation concerning the pressure trend, and the direction theintra-compartmental pressure is moving.

This collection of single data points over long periods of time isusually not very helpful because pressures within a compartment as wellas the patient's blood pressure can change abruptly, on the order ofminutes. Also, because of the pain associated with the needle measuringmethod noted above, the medical practitioner will seldom or rarely takepressure readings within a few minutes of each other using a needle.

A further problem of the needle measuring method is that for certainregions of the body, such as the lower leg, there are four compartmentsto measure. This means that a patient's leg must be stuck with the largebore needle at least four times in order for a medical practitioner torule out that a compartment syndrome exists for the lower leg. In thelower leg of the human body, one compartment is located under aneighboring compartment such that a needle measurement may be needed inat least two locations that are very close together, but in which themedical practitioner must penetrate tissues at a shallow depth at afirst location to reach the first compartment; and for reaching thesecond compartment that is underneath the first compartment, a largedepth must be penetrated by the needle, often with the needle piercingthe first compartment and then the second compartment.

Another problem, besides pain that is associated with the needlepressure measuring method, is that there is a lack of consensus amongmedical practitioners over the compartment pressure ranges which arebelieved to indicate that a compartment syndrome may exist for aparticular patient. Normal compartment pressure in the human bodyusually approaches 4 mmHg in the recumbent position. Meanwhile,scientists have found that an absolute pressure measurement of 30 mmHgin a compartment may indicate presence of compartment syndrome. However,there are other scientists who believe that patients withintracompartmental pressures of 45 mmHg or greater should be identifiedas having true compartment syndromes. But other studies have shownpatients with intra-compartmental pressures above these limits with noclinical signs of compartment syndrome. Additional studies have shownthat a pressure gradient based on perfusion pressure (diastolic bloodpressure minus intra-compartmental pressure) is the more importantvariable. Studies have shown in a laboratory setting that once theperfusion pressure drops to 10 mm Hg tissue necrosis starts to occur.

Other subjective methods for diagnosing compartment syndromes instead ofthe needle measuring method exist, however, they may have less accuracythan the needle measuring method because they rely on clinical symptomsof a patient. Some clinical symptoms of a patient used to help diagnosecompartment syndromes include pulselessness (absence of a pulse), lackof muscle power, pain, parastesias, and if the flesh is cold to touch.Pain out of proportion and with passive stretch are considered theearliest and most sensitive, but both have very low specificity. One ofthe major drawbacks of these symptoms is that for many of them thepatient must be conscious and must be able to respond to the medicalpractitioner. This is true for the muscle power and pain assessment. Forany inebriated patients or patients who are unconscious, the painassessment and muscle power assessment cannot be used accurately by themedical practitioner. In the setting of high energy trauma which isassociated with compartment syndrome, many patients are not capable ofcooperating with a good physical exam due to any number of causesincluding head trauma, medical treatment (including intubation), drug oralcohol ingestion, neurovascular compromise or critical and lifethreatening injuries to other body systems.

For the pain assessment, if a lower leg compartment syndrome exists in apatient, then the range of motion for a patient's foot or toes will beextremely limited and very painful when the patient's foot or toes areactively or passively moved. The pain from a compartment syndrome can bevery immense because the muscles are deprived of oxygen because of thecompartment syndrome.

Another drawback using pain to assess the likelihood of a compartmentsyndrome is that every human has a different threshold for pain. Thismeans that even if someone should be experiencing a high level of pain,he or she may have a high threshold for pain and therefore, not providethe medical practitioner with a normal reaction for the current level ofpain. Another problem with using pain to assess the likelihood of theexistence of a compartment syndrome is that if the patient isexperiencing trauma to other parts of their body, he or she may not feelthe pain of a compartment syndrome as significantly, especially if thetrauma to the other parts of the patient's body is more severe. Thiscondition is termed a distracting injury. On the other hand, traumacauses the initial injury that precipitates a compartment syndrome. Thatinitial trauma by definition will cause a baseline amount of pain thatis often very difficult to separate from a potential compartmentsyndrome pain. These initial injuries by themselves cause significantpain, so a patient that does not tolerate pain well may present similarto a compartment syndrome without having any increased pressures simplybecause they react vehemently to painful conditions.

Conventional Non-Invasive Techniques for Measuring Oxygenation Levels ofa Compartment

Non-invasive measuring of compartment syndromes using near infraredsensors, such as spectrophotometric sensors, to measure oxygenationlevels within a compartment has been suggested by the conventional art.However, these conventional techniques have encountered the problem of amedical practitioner locating compartments of interest and accuratelyand precisely positioning a sensor over a compartment of interest. Oftenthe orientation of the scan and the depth of the scan produced by a nearinfrared sensor as well as the orientation of a compartment can bechallenging for a medical practitioner to determine because conventionalsensors are not marked with any instructions or visual aids. Anotherproblem faced by the medical practitioner with conventional non-invasivetechniques is determining how to assess the oxygenation level ofcompartments that lie underneath a particular neighboring compartment,such as with the deep posterior compartment of the human leg.

In trauma settings, near infrared sensors often do not work when theyare placed over regions of the body that have hematomas or pools ofblood. In such conditions, a medical practitioner usually guesses atwhat regions of the human body do not contain any hematomas that couldblock compartment measurements. Also, conventional near infrared sensorstypically are not sterilized and cannot be used in surgical or operatingenvironments.

Near infrared sensors (NIRS) in their current form are limited to asingle sensor with a single sensor depth. They also can be affected byskin pigmentation that is not accounted for in the current technology.Placement of the sensor can be difficult since an expanding hematoma canblock a previously acceptable placement. Additionally, the only systemas of this writing is a single monitor system. There is no productavailable at this time which will allow for multiple areas to bemonitored in close proximity to one another without the potential forinterference from other sensor light sources.

Treatment for Compartment Syndrome

Referring now to FIG. 3, this figure is a side view of a human leg 100in which a surgical procedure, known as a fasciotomy, was performed inorder to release the pressures in one or more compartments surroundingthe bones of the leg according to a technique known in the art in orderto alleviate a compartment syndrome that was diagnosed. This surgicalprocedure includes an incision 300 that is made along the length of theleg 100 and is generally as long as the compartments contained withinthe leg 100. While a single incision 300 is illustrated in FIG. 3, asecond incision is made on the opposing side of the leg so that apatient will have two incisions on each side of his leg 100. Theseincisions typically extend from near the knee to near the ankle on eachside of the leg.

This procedure is very invasive and it often leaves the patient withsevere scars and venous congestion once healed. Also the procedureincreases a patient's chances of receiving an air-borne infectionbecause the incisions made on either side of the leg are usually leftopen for several days in order to allow for the swelling and excessbleeding to subside. Fasciotomies transform a closed fracture (one inwhich the skin is intact and minimal risk of infection) to an openfracture. Open fractures have a much higher risk of bone infectionswhich requires multiple surgical debridements and ultimately amputationin some cases in order to appropriately treat. Additionally, some woundcannot be closed and require skin transfers, or skin grafts, from otherparts of the body, usually from the anterior thigh.

Therefore, it is quite apparent that accurately diagnosing compartmentsyndrome is critical because any misdiagnosis can lead to significantmorbidity. A missed compartment syndrome can result in an insensate andcontracted leg and foot. A fasciotomy which is highly invasive procedureand which exposes a patient to many additional health risks should notbe performed in the absence of a compartment syndrome.

Additionally, time is an important factor in the evaluation of thesepatients. Ischemic muscle begins to undergo irreversible changes afterabout six hours of decreased perfusion. Once irreversible changes ornecrosis occur, a fasciotomy should not be performed. Fasciotomies inthe setting of dead muscle only increase the risk for severe infectionsand other complications. Late fasciotomies have been shown to haveapproximately a 50-75% risk of complication. Therefore, fasciotomiesneed to be performed early but judiciously in patients that are oftenunresponsive or uncooperative in order to prevent severe morbidity.

Accordingly, there is a need in the art for a non-invasive, real timemethod and system that monitors oxygenation levels of a compartment andthat is provided with sensors which can be precisely positioned over acompartment of interest in order to assist in assessing conditionsassociated with a compartment syndrome. A further need exists in the artfor a non-invasive method that monitors oxygenation levels of acompartment over long periods of time at frequent time intervals andthat can monitor different compartments that may be in close proximitywith one another. Another need exists in the art for oxygenation sensorsthat can be fabricated to fit the size of compartments of interest.There is also a need in the art for a non-invasive method and systemthat monitors oxygenation levels and that can identify ideal locationsalong a human body in which to conduct scans for deep compartments.There is another need in the art for sterile, non-invasive oxygenationsensors that can be used under surgical and operating conditions. Thereis a need for multiple locations and multiple compartments to bemonitored in a continual and orchestrated manner by a single system. Inother words, multiple monitors coordinated to limit noise andcontinually monitor multiple compartments are needed in the art.

SUMMARY OF THE INVENTION

A method and system for monitoring oxygenation levels in compartments ofan animal limb, such as in a human leg or a human thigh or a forearm,can be used to assist in the diagnosis of a compartment syndrome. Themethod and system can include one or more near infrared compartmentsensors in which each sensor can be provided with a compartmentalignment mechanism and a central scan depth marker so that each sensormay be precisely positioned over a compartment of a living organism,such as a compartment of a human leg or human thigh or forearm. Themethod and system can include a device for displaying oxygenation levelscorresponding to respective compartment sensors that are measuringoxygenation levels of a compartment of interest.

The alignment mechanism of a compartment sensor can include a linearmarking on a surface of the compartment sensor that is opposite to theside which produces a light scan used to detect oxygenation levels. Thelinear marking can be used by a medical practitioner to align acompartment sensor with the longitudinal axis of a compartment.

The central scan depth marker can include a linear marking positioned ona surface of a compartment sensor that intersects the alignmentmechanism, a crosshatch, at a location along the alignment mechanismthat denotes the deepest region of a light scan produced by thecompartment sensor. The depth of measurement can be displayed in numericform over the crosshatch guide to aid the clinician since depth variesbased on light source & receptor separation. The central scan depthmarker can insure that a medical practitioner properly aligns thecompartment sensor at a location that will measure a compartment ofinterest.

According to one exemplary embodiment of the invention, in addition toeach compartment sensor having a compartment alignment mechanism and acentral scan depth marker, the compartment sensors can be grouped inpairs and share a common supporting substrate. The common supportingsubstrate can include a separation device, such as, but not limited to,a perforated region. The separation device, such as a perforated region,can be torn or broken by the user in order to adjust for a size of acompartment of interest. In other words, with the separation device, apair of two compartment sensors can be physically divided so that thesensors do not share a common substrate after the separation device isutilized.

According to another exemplary embodiment of the invention, acompartment sensor can include one light emitting device and twodifferent sets of light detectors such that the compartment sensor canprovide a first, shallow oxygenation scan at a first depth and a second,deep oxygenation scan at a second depth. The second depth can be greaterthan the first depth, so that a general computing device coupled to thetwo compartment sensors can be programmed or hardwired to calculate thesecond, deep oxygenation level at the second depth by subtracting datagenerated by the first, shallow oxygenation level at the first depth.

According to another alternate exemplary embodiment of the invention,several individual compartment scanners can be grouped together along alongitudinal axis of a common supporting material to define a linearcompartment array. The linear compartment array can also include alinear marking on its surface that is opposite to the side whichproduces the light scan as well as multiple crosshatches for depthdenotation. The linear marking can be used to align the linearcompartment array with a longitudinal axis of a compartment.

According to another exemplary embodiment of the invention, acompartment sensor or compartment sensor array can be positioned at apredetermined position along a human leg in order to measure a deepposterior compartment of the human leg. Position is posteromedial to theposterior aspect of the tibia.

According to one exemplary embodiment of the invention, a linearcompartment sensor array can include individual sensors that scan atdifferent depths such that the linear compartment sensor array as awhole has a varied scan depth along its longitudinal axis to moreclosely match the topography, shape, or depth of a compartment ofinterest that has a corresponding varied depth. According to anotherexemplary embodiment of the invention, each individual compartmentsensor can produce its oxygenation scan at a predetermined interval suchthat each individual compartment sensor is only activated one at a timeor in a predetermined sequence so that any two or more sensors are notworking at a same instant of time in order to reduce any potential forlight interference among the different oxygenation scans produced byrespective sensors of the array.

According to a further exemplary embodiment of the invention, eachcompartment sensor can use optical filters in combination with differentwavelengths of light so that two or more compartment sensors can scan atthe same without interfering with one another. According to anotherexemplary embodiment of the invention, a linear compartment array caninclude optical transmitters that are shared among pairs of opticalreceivers. For example, a single optical transmitter can be used withtwo optical receivers that are disposed at angles of one-hundred eightydegrees relative to each other and the optical transmitter along theaxis of the compartment.

According to yet another exemplary embodiment, a compartment sensor orcompartment sensor array can be made from materials that can besterilized and used in operating environments that are free from germsor bacteria. A compartment sensor or compartment sensor array can alsobe provided with a coating that is sterilazable or sterilized. When acompartment sensor or compartment sensor array is sterilized, it can beprovided underneath bandages or dressings adjacent to a wound or injuryof a compartment or proximate to compartment of interest. Each sensorcan be provided with a common and sufficient length of cord, such as onthe order of approximately ten feet, to allow the cord to extend off thesterile operative field.

According to another exemplary embodiment of the invention, thecompartment monitoring method and system can include a device thatdisplays oxygenations levels of a compartment over time in whichoxygenation levels are measured at a particular time frequency, such as,but not limited to, on the order of seconds or minutes. According toanother exemplary embodiment of the invention, the compartmentmonitoring system and method can display all measured data from allsensors on the same screen. The display can also show a differentialbetween injured and uninjured leg values of the concordant compartments.

For example, the screen can display calculations of the differencebetween the values of the anterior compartment of both the injured legand the contralateral uninjured leg (control leg) to help evaluate theperfusion of the injured leg. According to an alternate exemplaryembodiment of the invention, the compartment monitoring system andmethod can display anatomical features and locations for positioning thesensors of the system along compartments of interest selected by a user.This program at initial set up can help insure proper placement of thesensor by the clinician by using diagrams for accurate placement foreach of the labeled sensors or sensor arrays.

According to another exemplary embodiment of the invention, thecompartment monitoring system can detect changes in a size of a hematomawhen at least one linear compartment array is used to measureoxygenations levels at different positions of a compartment.Alternatively, the compartment monitoring system can provide informationon various levels of blood flow along the longitudinal axis of acompartment when at least one linear compartment array is used tomeasure oxygenations levels at different positions of a compartment.

Alternatively, according to another exemplary embodiment of theinvention, a compartment sensor can be provided with a skin pigmentsensor that has a known reflectance and that can be used to calibratethe compartment sensor based on relative reflectance of skin pigmentwhich can affect data generated from oxygenation scans. For example, askin narrow-band simple reflectance device, a tristimulus colorimetricdevice, or scanning reflectance spectrophotometer can be incorporatedinto the oxygenation sensor system to obtain a standardized value forskin pigmentation which evaluate melanin and hemoglobin in the skin.

Once the skin melanin is determined it can be correlated to itscalculated absorption or reflectance (effect) on the NIRS value using apredetermined calibration system. This effect, optical density value,can be incorporated in tissue hemoglobin concentration calculations inthe deep tissue. Accounting for skin pigmentation will usually allow forinformation or values to be compared across different subjects withdifferent skin pigmentation as well as using the number as an absolutevalue instead of monitoring simple changes in value over time.

According to an exemplary embodiment of the invention, a compartmentsensor can be provided with layers of a known thickness and a knownabsorption in order to reduce the depth of an oxygenation scan by thesensor so that a thin layer of tissue, such as skin can be measured bythe sensor. In other words, due to limitations of how close the lightsource and receptor can be positioned, in order to evaluate verysuperficial layers such as skin, the sensor can be separated from theskin of the subject by fixed amount with a known material. For example,by using a material with a known optical density, the length of a scancan be shortened by projecting the light pathway mostly through theknown material.

The light pathway would escape the known material only at the maximumdepth to evaluate a limited depth of tissue such as skin. This techniquewould allow for direct measurement of the skin pigmentation effects onthe system. This skin sensor can be either incorporated into thecompartment monitoring system directly or used to construct thepredetermined calibration for skin reflectance values that can be usedby the compartment monitoring system.

According to another exemplary embodiment of the invention, thecompartment monitoring system can receive data from a blood pressuremonitoring system in order to correlate oxygenation levels with bloodpressure. The compartment monitoring system that includes a bloodpressure monitoring system can activate an alarm, such as an audible orvisual alarm (or both), when the diastolic pressure of a patient dropssince it has been discovered that perfusion can be significantly loweredor stopped at low diastolic pressures and when compartment pressures aregreater than the diastolic pressure.

According to another exemplary embodiment, the compartment monitoringsystem can increase a frequency of data collection for oxygenationlevels and/or blood pressure readings when low blood pressure isdetected by the system. According to an alternative exemplaryembodiment, the compartment monitoring system can display blood pressureand oxygenation levels simultaneously and in a graphical manner overtime, such as an X-Y plot in a Cartesian plane or as two separate graphsover time. Correlation between hemoglobin concentration and diastolicpressure can be used to estimate intra-compartmental pressures withouthaving to use invasive needle measurements.

According to another further exemplary embodiment, the inventive systemcan incorporate oxygenation levels from both lower extremities andcompare values between the legs or other body parts. Initial data frompatients with extremity injuries by the inventor have shown thatmuscular skeletal injuries cause hyperemia (increased blood flow andoxygen) in the injured extremity. If a compartment syndrome develops,the oxygenation drops from an elevated state to an equal and then lowerlevel with comparison to the uninjured limb. Therefore when comparinginjured and uninjured extremities, the injured limb may show increasedoxygenation levels. If levels begin to drop in the injured limb comparedto the uninjured limb, an alarm or alert can be triggered to alert theclinician. A display for the blood pressure being measured can also beprovided by the system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an X-ray view of a human leg with fractured bones ofthe tibia and fibula that lead to one or more compartment syndromes inmuscles surrounding the bones of the human leg.

FIG. 2 is a side view of a human leg in which compartment pressures arebeing measured with a large bore needle according to a conventionalmethod known in the prior art.

FIG. 3 is a side view of a human leg in which a surgical procedure,known as a fasciotomy, was performed in order to release the pressuresin one or more compartments surrounding the bones of the leg accordingto a technique known in the art.

FIG. 4 illustrates oxygen levels of compartments of a human leg beingmeasured by compartment sensors that include compartment alignmentmechanisms and central scan depth markers according to one exemplaryembodiment of the invention.

FIG. 5A illustrates a bottom view of two pairs of compartment sensorswith each sensor having a compartment alignment mechanism and a centralscan marker in addition to a separating device according to oneexemplary embodiment of the invention.

FIG. 5B illustrates a bottom view of the four compartment sensors ofFIG. 5A (?) but with the individual sensors divided from one anotherthrough using the separating device, such as the perforations, accordingto one exemplary embodiment of the invention.

FIG. 6A illustrates a bottom view of a three sensor embodiment in whichone sensor of the three compartment sensors can scan at two or moredepths according to one exemplary embodiment of the invention.

FIG. 6B, this figure illustrates the compartment sensor of FIG. 6A thatcan scan at two or more depths in order to measure deeper compartmentsof an animal body according to one exemplary embodiment of theinvention.

FIG. 7 illustrates a near light detector and a far light detector thatare positioned within substrate material at predetermined distances fromthe optical transmitter of a compartment sensor according to oneexemplary embodiment of the invention.

FIG. 8A illustrates a linear array of compartment sensors assembled as asingle mechanical unit that can provide scans at various depthsaccording to one exemplary embodiment of the invention.

FIG. 8B illustrates a linear compartment sensor array that can includeoptical transmitters that are shared among pairs of optical receiversaccording to one exemplary embodiment of the invention.

FIG. 8C is a functional block diagram of compartment sensor thatillustrates multiple optical receivers that may positioned on oppositesides of a single optical transmitter and that may be simultaneouslyactivated to produce their scans at the same time according to oneexemplary embodiment of the invention.

FIG. 9A illustrates a cross-sectional view of a left-sided human legthat has the four major compartments which can be measured by thecompartment sensors according to one exemplary embodiment of theinvention.

FIG. 9B illustrates a cross-sectional view of a right-sided human legand possible interference between light rays of simultaneous oxygenationscans made by the compartment sensors into respective compartments ofinterest according to one exemplary embodiment of the invention.

FIG. 9C illustrates a position of a compartment sensor in relation tothe knee for the deep posterior compartment of a right sided human legaccording to one exemplary embodiment of the invention.

FIG. 10 illustrates an exemplary display of numeric oxygenation valuesas well as graphical plots for at least two compartments of an animalaccording to one exemplary embodiment of the invention.

FIG. 11 illustrates single compartment sensors with alignment mechanismsand central scan depth markers that can be used to properly orient eachsensor with a longitudinal axis of a compartment of an animal bodyaccording to one exemplary embodiment of the invention.

FIG. 12 illustrates compartment sensor arrays with alignment mechanismsthat can be used to properly orient each array with a longitudinal axisof a compartment of an animal body according to one exemplary embodimentof the invention.

FIG. 13A illustrates various locations for single compartment sensorsthat can be positioned on a front side of animal body, such as a human,to measure oxygenation levels of various compartments according to oneexemplary embodiment of the invention.

FIG. 13B illustrates various locations for single compartment sensorsthat can be positioned on a rear side of animal body, such as a human,to measure oxygenation levels of various compartments according to oneexemplary embodiment of the invention.

FIG. 14A illustrates various locations for compartment sensor arraysthat can be positioned over compartments on a front side of an animalbody, such as a human, to measure oxygenation levels of the variouscompartments according to one exemplary embodiment of the invention.

FIG. 14B illustrates various locations for compartment sensor arraysthat can be positioned over compartments on a rear side of an animalbody, such as a human, to measure oxygenations levels of the variouscompartments according to one exemplary embodiment of the invention.

FIG. 14C illustrates an exemplary display and controls for the displaydevice that lists data for eight single compartment sensors according toone exemplary embodiment of the invention.

FIG. 14D illustrates an exemplary display of providing users withguidance for properly orienting a single compartment sensor over acompartment of an animal, such as a human leg, according to oneexemplary embodiment of the invention.

FIG. 15A illustrates a front view of lower limbs, such as two lower legsof a human body, that are being monitored by four compartment sensorarrays according to an exemplary embodiment of the invention.

FIG. 15B illustrates a display of the display device that can be used tomonitor hematomas and/or blood flow according to one exemplaryembodiment of the invention.

FIG. 16 illustrates a display of the display device for an instant oftime after the display of FIG. 15B and which can be used to monitorhematomas and/or blood flow according to one exemplary embodiment of theinvention.

FIG. 17 illustrates a sensor design for measuring the optical density ofskin according to one exemplary embodiment of the invention.

FIG. 18A illustrates a sensor that can penetrate two layers of skin toobtain optical density values according to one exemplary embodiment ofthe invention.

FIG. 18B illustrates a sensor that can penetrate one layer of skinaccording to one exemplary embodiment of the invention.

FIG. 18C illustrates a modified compartment monitoring system that cancorrelate skin pigmentation values with skin optical density values inorder to provide offset values for oxygenation levels across differentsubjects who have different skin pigmentation according to one exemplaryembodiment of the invention.

FIG. 19 is a functional block diagram of the major components of acompartment monitoring system that can monitor a relationship betweenblood pressure and oxygenation values according to one exemplaryembodiment of the invention.

FIG. 20 is an exemplary display that can be provided on the displaydevice and which provides current blood pressure values and oxygenationlevels of a compartment of interest according to one exemplaryembodiment of the invention.

FIG. 21 is a functional block diagram that illustrates sterilizedmaterial options for a compartment sensor according to one exemplaryembodiment of the invention.

FIG. 22 illustrates an exemplary clinical environment of a compartmentsensor where the sensor can be positioned within or between a dressingand the skin of a patient according to one exemplary embodiment of theinvention.

FIG. 23 is a graph of perfusion pressure plotted against oxygenationlevels of a study conducted to determine the sensitivity andresponsiveness of the inventive compartment monitoring system accordingto one exemplary embodiment of the invention.

FIG. 24 is a graph of perfusion pressure plotted against a change in theoxygenation levels from a baseline for each subject of the studyconducted to determine the sensitivity and responsiveness of theinventive compartment monitoring system according to one exemplaryembodiment of the invention.

FIG. 25 is a logic flow diagram illustrating an exemplary method formonitoring oxygenation levels of a compartment for detecting conditionsof a compartment syndrome.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A method and system for monitoring oxygenation levels in compartments ofan animal limb, such as in a human leg or a human thigh or a forearm,can be used to assist in the diagnosis of a compartment syndrome. Themethod and system can include one or more near infrared compartmentsensors in which each sensor can be provided with a compartmentalignment mechanism and a central scan depth marker so that each sensormay be precisely positioned over a compartment of a human leg or humanthigh or forearm. The method and system can include a device fordisplaying oxygenation levels corresponding to respective compartmentsensors that are measuring oxygenation levels of a compartment ofinterest.

Referring now to the drawings, in which like reference numeralsdesignate like elements, FIG. 4 illustrates oxygen levels 402A, 402B ofcompartments of a human leg 100 being measured by a near-infraredspectroscopy (NIRS) sensors 405A, 405B that include a compartmentalignment mechanisms 410A, 410B and central scan depth markers 415A,415B according to one exemplary embodiment of the invention.

The alignment mechanism 410 of a compartment sensor 405 can include alinear marking on a surface of the compartment sensor 405 that isopposite to the side which produces a light scan used to detectoxygenation levels. The linear marking can be used by a medicalpractitioner to align a compartment sensor 405 with the longitudinalaxis 450 of a compartment of interest. The invention is not limited to asolid line on the sensor 405. Other alignment mechanisms 410 within thescope of the invention include, but are not limited to, tick marks,dashed lines, notches cut in the substrate of the compartment sensor 405to provide a geometric reference for the medical practitioner, and otherlike visual orienting alignment mechanisms 405.

The central scan depth marker 415 can include a linear markingpositioned on a surface of a compartment sensor 405 that intersects thealignment mechanism 410 at a location along the alignment mechanism 410that denotes the deepest region of a light scan produced by thecompartment sensor 405. The depth of measurement can be displayed innumeric form over the central scan depth marker 415 as a guide to aidmedical practitioner since scan depth can vary based on the compartmentsensor's light source and receptor separation. The central scan depthmarker 415 can insure that a medical practitioner properly aligns thecompartment sensor 405 at a location that will measure a compartment ofinterest. Similar to the alignment mechanism 410 noted above, theinvention is not limited to a solid line on the compartment sensor 405.Other central scan depth markers 415 within the scope of the inventioninclude, but are not limited to, tick marks, dashed lines, notches cutin the substrate of the compartment sensor to provide a geometricreference for the medical practitioner, and other like visual orientingcentral depth markers 415.

Once the proper position for a compartment sensor 405 is determined bythe medical practitioner with the compartment alignment mechanism 410and the central scan depth marker 415, the medical practitioner canapply the compartment sensor 405 on the patient by using an adhesivethat is already part of the compartment sensor 405.

FIG. 4 illustrates three compartment sensors 405A, 405B, and 405C of asystem 400 for monitoring three different compartments of the lowerhuman leg 100. A fourth compartment sensor 405D not illustrated can bepositioned on a side of the leg not illustrated and which monitors thefourth compartment of the lower human leg 100. The compartment sensors405 illustrated in FIG. 4 and discussed throughout this document can beof the type described in U.S. Pat. No. 6,615,065 issued in the name ofBarrett et al. (the “'065 patent”), the entire contents of which arehereby incorporated by reference. The compartment sensors 405 caninclude those made and distributed by Somanetics, Troy, Mich. However,other conventional near infrared compartment sensors 405 can be usedwithout departing from the scope and spirit of the invention.

The compartment sensors 405 can generally provide spectrophotometric invivo monitoring of blood metabolites such as hemoglobin oxygenconcentration in any type of compartment and on a continuing andsubstantially instantaneous basis.

The compartment sensors 405 are coupled to a processor and display unit420 which displays the two oxygen levels 402A, 402B comprising thevalues of seventy-three. The processor and display unit 420 can displayall four oxygen levels of four compartments of the human leg 100 when atleast four compartment sensors 405 are deployed. The invention is notlimited to four compartment sensor embodiments. The invention caninclude any number of compartment sensors for the accurate detection ofconditions that may be associated with compartment syndrome. Forexample, another exemplary embodiment illustrated in FIG. 14C allows foreight sensor readings so that concomitant monitoring of thecontralateral uninjured leg can be performed.

The processor of the display unit 420 can be a conventional centralprocessing unit (CPU) known to one of ordinary skill in the art. It mayhave other components too, similar to those found in a general purposecomputer, such as, but not limited to, memory like RAM, ROM, EEPROM,Programming Logic Units (PLUs), firmware, and the like. Alternatively,the processor and display unit 420 can be a general purpose computerwithout departing from the invention.

The processor and display unit 420 can operate in a networked computerenvironment using logical connections to one or more other remotecomputers. The computers described herein may be personal computers,such as hand-held computers, a server, a client such as web browser, arouter, a network PC, a peer device, or a common network node. Thelogical connections depicted in the Figures can include additional localarea networks (LANs) and a wide area networks (WANs) not shown.

The processor and display unit 420 illustrated in FIG. 4 and theremaining Figures may be coupled to a LAN through a network interface oradaptor. When used in a WAN network environment, the computers maytypically include a modem or other means for establishing directcommunication lines over the WAN.

In a networked environment, program modules may be stored in remotememory storage devices. It will be appreciated that the networkconnections shown are exemplary and other means of establishing acommunications link between computers other than depicted may be used.

Moreover, those skilled in the art will appreciate that the presentinvention may be implemented in other computer system configurations,including other hand-held devices besides hand-held computers,multiprocessor systems, microprocessor based or programmable consumerelectronics, networked personal computers, minicomputers, mainframecomputers, and the like.

The invention may be practiced in a distributed computing environmentwhere tasks may be performed by remote processing devices that arelinked through a communications network. In a distributed computingenvironment, program modules may be located in both local and remotestorage devices.

The processor and display unit 420 can comprise any general purposecomputer capable of running software applications and that is portablefor mobile applications or emergency applications.

The communications between the processor and display unit 420 and thesensors 405 can be wire or wireless, depending upon the application.Typical wireless links include a radio frequency type in which theprocessor and display unit 420 can communicate with other devices usingradio frequency (RF) electromagnetic waves. Other wireless links thatare not beyond the scope of the invention can include, but are notlimited to, magnetic, optical, acoustic, and other similar wirelesstypes of links.

In the exemplary embodiment illustrated in FIG. 4, the compartmentsensors 405 are coupled to the processor and display unit 420 withcables 430A, 430B which can include electrical conductors for providingoperating power to the light sources of the compartment sensors 405 andfor carrying output signals from the detectors of the sensors 405 to thedisplay unit 420. The cables 430 may be coupled to a quad-channelcoupler, a preamplifier 425A, 425B, and an integrated, multipleconductor cable 435. Alternatively, all wires could be packaged ormerged into a single unit or cord or plug (not illustrated) forinsertion into the monitor for ease of management for the clinician andto prevent misplacement of wire plugs into wrong sockets.

In addition to tracking compartment oxygen levels, the processor anddisplay unit 420 may receive data from a blood pressure monitor 445. Theblood pressure monitor 445 may be coupled to a probe 440 that takespressure readings from the patient at one or more locations, such as,but not limited to, an arm with a cuff, a needle in the volar wrist, thebrachium (arm) via a sphygmomanometer, or arterial line. The probe 440can be any one of a number of devices that can take blood pressurereadings, such as, but not limited to, automated inflating pressurecuffs (sphygmomanometer), arterial lines, and the like. Similarly, othertypes of blood pressure monitors 445 are not beyond the scope of theinvention. Further details of the relationship between blood pressureand oxygen levels in the human body will be discussed and described morefully below in connection with FIGS. 19-20.

The display and processing unit 420 can display values at any one timefor all compartment sensors 405 being used. While the display andprocessing unit 420 only displays two oxygen levels for the embodimentillustrated in FIG. 4, the display and processing unit 420 could easilydisplay all four values from the four compartment sensors 405 that arebeing used to monitor the four compartments of the lower leg 100.

Referring now to FIG. 5A, this figure illustrates a bottom view of twopairs of compartment sensors 405 with each sensor 405 having acompartment alignment mechanism 410 and a central scan marker 415 inaddition to a separating device 505 according to one exemplaryembodiment of the invention. The substrate 530 of each compartmentsensor 405 can comprise a foam or plastic material that may have a softand comfortable outer layer. The separating device 505 is illustratedwith a dashed line in FIG. 5A.

According to one exemplary embodiment the separating device 505 cancomprise a perforation in the substrate 530. A perforation is a seriesof cuts or removed portions positioned along a line which can beperforated or separated. This means, for the exemplary embodimentillustrated in FIG. 5A, the first compartment sensor 405A can bephysically separated from the second compartment sensor 405B. Theseparating device 505 is not limited to perforations and it can includeother types of devices. For example, the separating device 505 cancomprise a zipper, a plastic seal line, hook and loop fasteners andother like devices that would permit the rapid and accurate expansion ofcompartment sensors 405 when used in a trauma setting.

As noted above, the compartment sensors 405 can include alignmentmechanisms 410 and a central scan depth marker 415 in order toaccurately position the compartment sensors 405 over compartments ofinterest. The alignment mechanisms 410 and central depth markers 415 areillustrated with dashed or dotted lines because they are “hidden”relative to the bottom view of the compartment sensors 405 which areillustrated in FIG. 5A.

Each compartment sensor 405 may comprise an optical transmitter 510 andan optical receiver 515. The optical transmitter 510 may comprise anelectrically actuated light source for emitting a selected examinationspectra. Specifically, the optical transmitter 510 may comprise two ormore narrow-bandwidth LEDs whose center output wavelengths correspond tothe selected examination spectra. Each optical receiver 515 may comprisetwo or more light detectors, such as photodiodes. In the embodimentillustrated in FIG. 5A, the optical receiver 515 has a total of fourphotodiodes in which pairs of photodiodes work together to provide a“near” detector and a “far” detector. Each photo diode must have tworeceptors to receive light at two separate wavelengths to allow forcalculations of oxy-hemoglobin and deoxy-hemoglobin concentrations.Using two pairs of receptors allows for a deep and shallow set to enableisolation of only the deep tissue oxygenation (see FIG. 7).

Referring briefly now to FIG. 7, the “near” light detector 702B and the“far” light detector 702A are positioned within the substrate material530 at predetermined distances from the optical transmitter 510. The“near” detector 702B formed by the two photodiodes that are closest tothe optical transmitter 510 have a light mean path length 710B which isprimarily confined to “shallow” layers 705 of a compartment of interest.Meanwhile, the “far” detector 702A formed by the pair of photodiodesthat are farthest from the optical transmitter 510 have a light meanpath 710A that is longer than that of the “near” detector and isprimarily confined to “deep” layers of a compartment of interest in aleg 100.

By appropriately differentiating the information from the “near” or“shallow” detector 702B (which may produce a first data set) from the“far” or “deep” detector 702A (which may produce a second data set), aresultant value for the tissue optical density may be obtained thatcharacterizes the conditions within a compartment of interest withoutthe effects that are attributable to the overlying tissue 705 which isadjacent to the compartment of interest.

This enables the compartment monitoring system 400 (illustrated in FIG.4) to obtain metabolic information on a selective basis for particularregions within the patient and by spectral analysis of the metabolicinformation and by using appropriate extinction coefficients, anumerical value or relative quantified value such as 402 of FIG. 4 maybe obtained which can characterize metabolites or other metabolite data,such as the hemoglobin oxygen saturation, within the particular regionof interest. This region of interest is defined by the curved light meanpath 710A extending from the optical transmitter 510 to the “far” or“deep” detector 702A and between this path 710A and the outer peripheryof the patient but excluding the region or zone defined by the curvedlight mean path 710B extending from the optical transmitter 510 to the“near” or “shallow” detector 26. Further details of the compartmentsensors 405 are described in U.S. Pat. No. 6,615,065, issued in the nameof Barrett et al., which is hereby incorporated by reference.

Referring back now to FIG. 5A, each compartment sensor 405 has its owncable 430 that provides power to the optical transmitter 405A and thatreceives data from the optical receiver 515. Each compartment sensor 405may also include a label 555 which may comprise a name and an anatomicallocation to position the compartment sensor 405 on a patient. This labelmay be placed on the bottom of the sensor 405 that contacts the patientas well as on the side that is opposite to the side which contacts thepatient. For example, the first sensor 405A can have a first label 555Athat comprises the phrase, “Lateral” to describe the name of thecompartment that this compartment sensor 405A that is designed toassess. The numerical depth can also be displayed on the label, but isnot limited to a single depth.

The first pair of compartment sensors 405A, 405B may be coupled to thesecond pair of compartment sensors 405C, 405D with an expansion device535. The expansion device 535 may comprise an elastic material thatstretches. The expansion device 535 allows the pair of compartmentsensors 405 to be positioned on appropriate parts of a patient tomonitor any compartments of interest. The four compartment sensorexemplary embodiment illustrated in FIG. 5A is designed for the fourcompartments of a human lower leg 100.

The expansion device 535 is not limited to elastic material. Theexpansion device can include other mechanisms which allow for anadjustable separation between the pairs of compartment sensors 405 sothat the compartment sensors 405 may be precisely and appropriatelypositioned over specific compartments of interest. The expansion device535 may include, but is not limited to, springs, tape, hook and loopfasteners, gauze, and other like materials.

Referring now to FIG. 5B, this figure illustrates a bottom view of thefour compartment sensors 405 of FIG. 5A but with the individual sensors405 divided from one another through using the separating device 505,such as the perforations, according to one exemplary embodiment of theinvention. Specifically, the first compartment sensor 405A of the firstpair of sensors 405A, 405B is physically located away from the secondcompartment sensor 405B. Similarly, the third compartment sensor 405C ofthe second pair of sensors 405B, 405C is physically located away fromthe fourth compartment sensor 405C. The separating device 505, theexpansion device 535 in combination with the alignment mechanism 410 andcentral scan depth marker 415 can allow the compartment sensors 405 tobe accurately and precisely positioned over compartments of interest,such as the four compartments of a human leg 100. In order to accuratelymonitor the appropriate compartment, a right and left configuration canbe provided since compartment alignment would be reversed based on whichleg is examined by the medical practitioner. Each configuration would belabeled as right or left. The configuration illustrated in FIGS. 5A and5B are designed for human left leg 100 where the expansion device wouldbe positioned over the tibia.

Referring now to FIG. 6A, this figure illustrates a bottom view of athree sensor embodiment in which one sensor 605 of the three compartmentsensors 405A, 405B, 605 can scan at two or more depths according to oneexemplary embodiment of the invention. Specifically, a compartmentsensor 605 may include an optical transmitter 510C that works with atleast two different optical receivers 515C1 and 515C2. As noted above,each optical receiver 515 may comprise two or more light detectors, suchas photodiodes. In the embodiment illustrated in FIG. 6A, each opticalreceiver 515C1 and 515C2 has a total of four photodiodes in which pairsof photodiodes work together to provide “near” detector and “far”detectors for a respective receiver 515C1, 515C2. This combinationallows the compartment sensor 605 to scan at least two different depths.And because of the capability to scan at two different depths, thecompartment sensor 605 is provided with two different central scan depthmarkers 415C1, 415C2.

Referring now to FIG. 6B, this figure illustrates the compartment sensor605 of FIG. 6A that can scan at two or more depths in order to measuredeeper compartments of an animal body according to one exemplaryembodiment of the invention. The two optical receivers 515 of FIG. 6Bwork in principal in an identical manner relative to the opticalreceiver described in connection with FIG. 7 discussed above. This meansthat the combination of the optical transmitter 510C and opticalreceiver 515C1 can provide an oxygenation level for a first scan depth620B of a patient. Meanwhile, the combination of the optical transmitter510C and the optical receiver 515C2 can provide an oxygenation level fora second scan depth 620A of a patient.

Therefore, this stacked compartment sensor 605 can be used to measurethe oxygenation level of a first compartment that may be positionedunderneath a second compartment, such as for the deep posteriorcompartment of a lower leg 100 of a human body which is positionedbeneath the superficial posterior compartment of the leg 100. Thisstacked compartment sensor 605 can allow the display and processing unit420 to subtract the oxygenation level found at the first scan depth 620Bof the first compartment, such as the superficial posterior compartment,from the oxygenation level at the second scan depth 620A of the secondcompartment, such as the deep posterior compartment.

The invention is not limited to the two stacked optical receiverembodiment 605 illustrated FIGS. 6A and 6B, and can include any numberof optical receivers 515 positioned in the substrate material 530 sothat various scan depths can be made to determine oxygenation levelswithin multiple compartments that may be stacked on or positionedadjacent to one another in a sequential or layered, shallow to deeparrangement.

Referring now to FIG. 8A, this Figure illustrates a linear array 805 ofcompartment sensors 405 assembled as a single mechanical unit that canprovide scans at various depths 620A, 620B, 620C, and 620D. Thecompartment sensors 405 can be simultaneously activated to produce theirscans of various depths 620 at the same time when optical filters areused as will be described more fully below in connection with FIG. 8C.Alternatively, the sensors 405 of the linear array 805 can produce theirscans of various depths 620 by controlling a phase or timing of theactivation of the sensors 405 so that no two sensors 405 are activatedat the same time in order to reduce any potential of opticalinterference between the sensors 405. This phasing of the sensors can becontrolled by the display and control unit 420 of FIG. 4.

The first compartment sensor 405A can provide a first scan depth 620Athat is shorter or more shallow than a second scan depth 620B producedby the second compartment sensor 405B. The scan depths 620 can increasein this manner along its longitudinal axis which corresponds with itsalignment mechanism 410 so that the linear array 805 matches the one ormore depths of a single compartment of interest. As noted above inconnection with FIG. 6B, the scan depth 620 of a compartment sensor 405is function of the separation distance between the optical transmitter510 and optical receiver 515. For example, a scan depth 620 of acompartment sensor 405 can be decreased as the optical receiver 515 ismoved closer along the body of the sensor 405 towards the opticaltransmitter 510C.

One of ordinary skill in the art recognizes that many of thecompartments of the human body have various different geometries andresulting depths relative to the outside skin of a patient. For example,the compartments of the lower human leg 100 tend to have a greater depthor volume adjacent to the knee and generally taper or decrease in depthtowards the ankle or foot. Therefore, linear arrays 805 of compartmentsensors 405 can be designed to have depths that match a particulargeometry of a compartment of interest. To achieve these different scandepths 620, each compartment sensor 405 can have an optical transmitter510 and an optical receiver 515 that is spaced or separated from eachother by an appropriate distance to achieve the desired scan depth 620.If a compartment of interest has a substantially “flat” or “linear”depth relative to the skin surface of a patient, the linear array 805can be designed such that each compartment sensor 405 produces scanswith uniform depths (not illustrated) to match a compartment with such alinear or flat geometry.

Like the single sensor embodiments described above in FIGS. 4-6A whichare designed to measure individual compartments, the compartment sensorarray 805 may comprise an alignment mechanism 410 that can be positionedso that it corresponds with the longitudinal axis 450 of a particularcompartment. The compartment sensor array 805 of FIG. 8A is not providedwith any central depth markers 415 like those of the single sensorembodiments since the depth markers 415 may not be needed by the medicalpractitioner since he or she will be assessing the entire length of aparticular compartment with the entire compartment sensor array 805which is unlike that of the single sensor embodiments. Alternatively,multiple crosshatches and numerical depths (not illustrated) can bepositioned over each light source/receptor set to locate where eachmeasurement is obtained for identifying sites of a hematoma, which willbe described in more detail in connection with FIGS. 15-16 below.Additionally, these positions could be used to locate appropriateamputation level for diabetics or peripheral vascular disease, which isalso described in more detail in connection with FIGS. 15-16 below.

Referring now to FIG. 8B, this figure illustrates a linear compartmentsensor array 805 that can include optical transmitters 510 that areshared among pairs of light receptors 515. For example, a single opticaltransmitter 510A1 can produce light rays 820A, 820B that can be used bytwo optical receivers 515A1, 515A2 that are disposed at angles ofone-hundred eighty degrees relative to each other and the opticaltransmitter 510A1 along the longitudinal axis and alignment mechanism410A of the compartment sensor array 805A. As described previously, thelight source and receptor separation can be varied to best match thetopography of the compartment in the leg or other body part. Largerseparation would allow for deeper sampling in the proximal leg versusmore shallow depth closer to the ankle.

As discussed above in connection with the single sensor array 805 ofFIG. 8A, the sensors 405 of each compartment sensor array 805illustrated in FIG. 8B can be simultaneously activated to produce theirscans at the same time when optical filters (not illustrated in FIG. 8B)are used as will be described more fully below in connection with FIG.8C. Alternatively, the sensors 405 of each linear compartment sensorarray 805 can produce their scans by controlling a phase or timing ofthe activation of the sensors 405 so that no two sensors 405 areactivated at the same time in order to reduce any potential for opticalinterference between the sensors 405. This phasing of the sensors can becontrolled by the display and control unit 420 of FIG. 4.

Like the single sensor embodiment illustrated in FIG. 5A, thecompartment sensor array 805 of FIG. 8B can comprise an alignmentmechanism 410 for aligning the structure with the longitudinal axis 450of a compartment as well as a separation device 505A that can be used todivide the physical structure of the paired array 805A, 805B into twoseparate linear compartment sensor arrays 805A, 805B. The compartmentsensor arrays 805 of FIG. 8B may also include labels 555 and anexpansion device 535, like those of FIG. 5A. The labels can bepositioned on the front and back sides of each compartment sensor array805. While the optical transmitters 510 and receivers 515 of FIG. 8B areillustrated in functional block form, it is noted that these elements aswell as other numbered elements, which correspond to the numberedelements of FIGS. 4-7, work similar to the embodiments described andillustrated in FIGS. 4-7.

Referring now to FIG. 8C, this figure is a functional block diagram ofcompartment sensor 405 that illustrates multiple optical receivers 515that may positioned on opposite sides of a single optical transmitter510 and that may be simultaneously activated to produce their scans atthe same time. This exemplary embodiment can produce scans at the sametime by using light with different wavelengths. Using light withdifferent wavelengths can help reduce and substantially eliminate anyoptical interference that can occur between multiple light rays that maybe received by the multiple optical receivers 515. While the opticalreceivers 515 of FIG. 8C are illustrated in functional block form, it isnoted that these receivers 515 as well as other numbered elements, whichcorrespond to the elements of FIGS. 4-7, work similar to the embodimentsdescribed and illustrated in FIGS. 4-7.

The two optical receivers 515A1, 515A2 of FIG. 8C may be simultaneouslyactivated when two optical filters 810A, 810B having differentwavelengths are used. The first optical filter 810A may have a firstwavelength of lambda-one (.lamda.1) which is different than a secondwavelength of lambda-two (.lamda.2) that is the wavelength of the secondoptical filter 810B1. The optical transmitter 510 can be designed toproduce light having wavelengths of the first and second wavelengthswhich correspond with the first and second optical filters 810A, 810B.

Light 820A with a first wavelength can be produced by the opticaltransmitter 510 propagating its light through a first optical filter810A1 that is designed to only let the first wavelength pass through it.Similarly, Light 820B with a second wavelength can be produced by theoptical transmitter 510 propagating its light through a second opticalfilter 810B1 that is designed to only let the second wavelength passthrough it. A third optical filter 810A2 corresponding with the firstoptical filter 810A1 can be designed to only pass the first wavelengthsuch that the optical receiver 515A1 only detects light of the firstwavelength. Similarly, a fourth optical filter 810B2 corresponding withthe second optical filter 810B1 can be designed to only pass the secondwavelength such that the optical receiver 515A2 only detects light ofthe second wavelength.

In this way, simultaneous different compartment scans can be produced atthe same time with light having the first wavelength of lambda-one(.lamda.1) and light having the second wavelength of lambda-two(.lamda.2), in which the two optical receivers 515A1 and 515A2 share thesame optical transmitter 510. This principal of optical receivers 515sharing the same optical transmitter 510 is also illustrated in FIG. 8Bwhich provides the compartment sensor arrays 805 discussed above.Specifically, any optical transmitter 510/optical receiver 515 groupthat is positioned along a single alignment mechanism 410 andlongitudinal axis 450 can be designed to have a unique wavelengthrelative to its neighbors along the same line. So this means that eachoptical transmitter 510/optical receiver 515 group of a particularcompartment sensor array 805, such as first array 805A, can be designedto have unique wavelengths relative to each other for illuminating thesame compartment. Meanwhile, a neighboring compartment sensor array 805,such as second array 805B, may have the same wavelength arrangement asthe first array 805A.

One of ordinary skill in the art recognizes that each light opticaltransmitter and optical receiver design uses two separate wave lengthsto solve for oxy-hemoglobin and deoxy-hemoglobin concentrations, asillustrated in FIG. 7. Therefore, the two optical wavelength designdescribed for FIG. 8C above may translate into four or more wavelengthsfor each optical transmitter 510 and pair of optical receivers 515. Thetwo wavelength design for FIG. 8C was described above for simplicity andto illustrate how groups of optical transmitters and optical receiverscan operate at different wavelengths relative to the groupings.

The invention is not limited to only two optical receivers 515 thatshare the same optical transmitter 510. The invention could includeembodiments where a single optical transmitter 510 is shared by aplurality of optical receivers 515 greater than two relative to theexemplary embodiment illustrated in FIG. 8C.

Referring now to FIG. 9A, this figure illustrates a cross-sectional viewof a left-sided human leg 100 that has the four major compartments 905which can be measured by the compartment sensors 405 according to oneexemplary embodiment of the invention. A first compartment 905B (alsonoted with a Roman Numeral One) of the lower human leg 100 comprises theanterior compartment that is adjacent to the Tibia 910 and Fibula 915. Afirst compartment sensor 405B is positioned adjacent to the anteriorcompartment 905B and provides a first oxygenation scan having a depth of620B.

A second compartment 905A (also noted with a Roman Numeral Two) of thelower human leg 100 comprises the lateral compartment that is adjacentto the Fibula 915. A second compartment sensor 405A is positionedadjacent to the lateral compartment 905A and provides a secondoxygenation scan having a depth of 620A.

A third compartment 905D (also noted with a Roman Numeral Three) of thelower human leg 100 comprises the superficial posterior compartment thatis behind the Tibia 910 and Fibula 915. A third compartment sensor 405Dis positioned adjacent to the posterior compartment 905D and provides athird oxygenation scan having a depth of 620D.

A fourth compartment 905C (also noted with a Roman Numeral Four) of thelower human leg 100 comprises the deep posterior compartment that iswithin a central region of the human leg 100. A fourth compartmentsensor 405C is positioned adjacent to the deep posterior compartment905C and provides a fourth oxygenation scan having a depth of 620C.

Referring now to FIG. 9B, this figure illustrates a cross-sectional viewof a right-sided human leg 100 and possible interference between lightrays 820 of simultaneous oxygenation scans made by the compartmentsensors 405 into respective compartments of interest according to oneexemplary embodiment of the invention. This figure illustrates how lightrays 820 produced by respective compartment sensors 405 can interferewith one another. To resolve this potential problem, the activation andhence, production of light rays 820, by the compartment sensors 405 canbe phased so that light rays 820 produced by one compartment sensor 405Aare not received and processed by a neighboring compartment sensor 405B,405C. When light is emitted from the compartment sensors 405 throughtissue, the light does not travel in a straight line. It is reflectedand spreads throughout the whole tissue. Therefore, light interferenceor noise would be a significant concern for multiple light sourcesplaced in close proximity to each other. Alternatively, and as notedabove, each compartment sensor 405 can produce optical wavelengths thatare independent of one another in order to reduce any chances of opticalinterference.

Referring now to FIG. 9C, this figure illustrates a position 930 of acompartment sensor 405C in relation to the knee 927 for the deepposterior compartment 905C of a right sided human leg 100 according toone exemplary embodiment of the invention. As illustrated in FIGS. 9Aand 9B discussed above, the deep posterior compartment sensor 405C canbe positioned such that the sensor 405C can directly sense theoxygenation levels of this compartment 905C without penetrating or goingthrough another compartment. With respect to FIG. 9C, the deep posteriorcompartment 905C can be accessed by placing the sensor along theposteromedial aspect of the medial tibia. In other words, palpation ofthe shin bone will allow the location of the tibia. The sensor 405should be placed just behind the bone on the inside of the leg along thelongitudinal axis 450C of the compartment 905C (not illustrated in thisFigure). The compartment sensor 405C can be aligned with thelongitudinal axis 450C of the deep posterior compartment 905C throughusing the alignment mechanism 410C. The compartment sensor 405C canpositioned at any point along the longitudinal axis 450C. The locationof this deep posterior compartment sensor 405C on the lower leg 100 maybe one inventive aspect of the technology since it allows a direct scanof the deep posterior compartment 905C.

Referring now to FIG. 10, this figure illustrates an exemplary display1000 of numeric oxygenation values 402 as well as graphical plots 1005for at least two compartments of an animal according to one exemplaryembodiment of the invention. The graphical plots 1005 can display thecurrent instantaneous oxygenation level for each compartment as a pointas well as historical data displayed as other points along a line thatplots the history for a particular compartment sensor 405. In otherwords, the X-axis of the plots 1005 can denote time in any incrementswhile the Y-axis of the plots can denote oxygenation levels monitored bya particular sensor 405.

While only two plots are illustrated, multiple plots can be displayedfor each respective sensor 405. In compartment sensor array 805deployments, the graphical plot 1005 can represent an “average” ofoxygenation levels measured by the multiple sensors of a particularlinear compartment sensor array 805. The display device 420 can includecontrols 1015 that allow for the selection of one or more compartmentsensors 405 or one or more compartment sensor arrays 805 for displayingon the display device 420. The display of historical oxygenation levelsof a compartment 905 over time through the plots 1005 is a significantimprovement over conventional methods of direct pressure readings ofcompartments 905 which usually would only allow periodic measurements ofcompartments 905 on the order of every fifteen or thirty minutescompared to minutes or seconds now measured with the compartment sensors405 described in this document.

Referring now to FIG. 11, this figure illustrates single compartmentsensors 405 with alignment mechanisms 410 and central scan depth markers415 that can be used to properly orient each sensor 405 with alongitudinal axis 450 of a compartment 905 of an animal body accordingto one exemplary embodiment of the invention. While the longitudinalaxis 450 of a compartment (shown with broken lines) cannot actually beseen on the external surface of a lower human leg 100 by a medicalpractitioner, a medical practitioner can envision this invisible axis450 based on the anatomy of the leg, such as looking at the knee 927 andcomparing its orientation with the ankle and foot of the leg 100. Asdescribed above, the compartment extends from the knee to ankle and thesensor can be placed over a portion or all of the compartment beingmeasured. With these single compartment sensor 405 embodiments, eachsensor 405 can be positioned along the length of the longitudinal axis450 to obtain an oxygenation level for a particular compartment 905 ofinterest.

Referring now to FIG. 12, this figure illustrates compartment sensorarrays 805 with alignment mechanisms 410 that can be used to properlyorient each array 805 with a longitudinal axis 450 of a compartment 905of an animal body according to one exemplary embodiment of theinvention. Since compartment sensor arrays 805 will typically occupyclose to the entire length of any given longitudinal axis 450 of acompartment 905 of interest, the individual sensors 405 of thecompartment sensor array 805 are usually not provided with central scandepth markers 415. In the sensor array embodiments, the arrays 805 areusually provided only with the alignment mechanism 410. However, thecentral scan depth markers 415 could be provided if desired for aparticular application or medical practitioner (or both).

Referring now to FIG. 13A, this Figure illustrates various locations forsingle compartment sensors 405 that can be positioned on a front side ofanimal body, such as a human, to measure oxygenation levels of variouscompartments 905 according to one exemplary embodiment of the invention.FIG. 13A illustrates that the invention is not limited to compartmentsensors 405 that only measure lower legs 100 of the human body. Thecompartment sensors 405 can measure various different compartments 905such as, but not limited to, compartments 905 of the arm, thighs, andabdomen.

Referring now to FIG. 13B, this Figure illustrates various locations forsingle compartment sensors 405 that can be positioned on a rear side ofanimal body, such as a human, to measure oxygenation levels of variouscompartments 905 according to one exemplary embodiment of the invention.Similar to FIG. 13A above, the compartment sensors 405 shown in thisFigure can measure various different compartments 905 such as, but notlimited to, compartments 905 of the arm, thighs, and abdomen. Also,while grouped compartment sensors 405 that are coupled together withexpansion devices 535 are not illustrated here (such as those describedin connection with FIG. 5A above), one of ordinary skill recognizes thatsuch grouped compartment sensors can be substituted anywhere were thesingle compartment sensors 405 are shown.

Referring now to FIG. 14A, this Figure illustrates various locations forcompartment sensor arrays 805 that can be positioned over compartments905 on a front side of an animal body, such as a human, to measureoxygenation levels of the various compartments 905 according to oneexemplary embodiment of the invention. Like the single compartmentsensor embodiments of FIGS. 13A-13B described above, the compartmentsensor arrays 805 can measure various different compartments 905 suchas, but not limited to, compartments 905 of the arm, thighs, andabdomen.

Referring now to FIG. 14B, this Figure illustrates various locations forcompartment sensor arrays 805 that can be positioned over compartments905 on a rear side of an animal body, such as a human, to measureoxygenations levels of the various compartments 905 according to oneexemplary embodiment of the invention. Also, while grouped compartmentsensor arrays 805 that are coupled together with expansion devices 535are not illustrated here (such as those described in connection withFIG. 8B above), one of ordinary skill recognizes that such groupedcompartment sensor arrays 805 can be substituted anywhere were theindividual compartment array sensors 805 are shown.

Referring now to FIG. 14C, this Figure illustrates an exemplary display1300 and controls for the display device 420 that lists data for eightsingle compartment sensors 405 according to one exemplary embodiment ofthe invention. The eight single compartment sensors 405 may bemonitoring compartments of two limbs of an animal, such as two lowerlegs of a human patient. One limb is usually uninjured while the otherlimb is typically injured, though the system is not limited tounilateral injuries.

The display 1300 may provide up to eight different plots or graphs1335A, 1330A, 1325A, 1320B, 1335B, 1330B, 1325B, 1320B of data that aretaken from the eight different sensors 405 or sensor arrays 805. Thefirst pair of right and left leg sensors may monitor the anteriorcompartment 905B of FIG. 9A which is displayed with the letter “A” forthe first row 1335 of data. The second pair of right and left legsensors may monitor the lateral compartment 905A of FIG. 9A which isdisplayed with the letter “L” for the second row 1330 of data. The thirdpair of right and left leg sensors may monitor the deep posteriorcompartment 905C which is displayed with the letters “DP” for the thirdrow 1325 of data. The first pair of right and left leg sensors maymonitor the superficial posterior compartment 905D which is displayedwith the letters “SP” for the fourth row 1320 of data.

The display 1300 may also provide a measure of a difference 1340 inoxygenation levels between the injured limb or region and the uninjuredlimb or region. This difference may be displayed by listing the twooxygenation levels of each respective limb separated by a slash “/”line. Underneath the two oxygenation levels for a respective pair ofsensors for the injured and uninjured limbs, a value which is thedifference between the oxygenation levels displayed above it may belisted. For example, for the first oxygenation difference value of1340A, the oxygenation level for the right leg sensor is the value offorty-four while the value for the left leg sensor is the value ofsixty-five. In this exemplary embodiment, the right leg is injured whilethe left leg is uninjured. The difference value displayed under the twooxygenation levels for the first data set 1340A is twenty-one.

Initial data from patients with extremity injuries measured by theinventor have shown that muscular skeletal injuries cause hyperemia(increased blood flow and oxygen) in the injured extremity. If acompartment syndrome develops, the oxygenation drops from an elevatedstate to an equal and then lower level with comparison to the uninjuredlimb. Therefore when comparing injured and uninjured extremities, theinjured limb should show increased oxygenation levels. If levels beginto drop in the injured limb compared to the uninjured limb, an alarm oralert can be triggered to warn the medical practitioner. This alarm canbe visual or audible (or both).

With the display 1300, a medical practitioner can modify how data isdisplayed by pressing the “mode” button 1305 on the display 1300 (whichmay comprise a “touch-screen” type of display). The mode button 1305permits the medical practitioner to change the display of the screen.This function would allow for selection between multiple differentsettings to allow for data downloading, changing the time frame forwhich data is displayed, etc. With the time mark “button” 1310, themedical practitioner can mark or “flag” certain data points beingmeasured for later review. With the select “button” 1315, the medicalpractitioner can select between the multiple options that can beaccessed through the mode button.

While the above description of FIG. 14C mentioned that eight singlecompartment sensors 405 produced the data of the display 1300 of FIG.14C, the single compartment sensors 405 can be easily substituted bycompartment sensor arrays 805. In such a scenario in which compartmentsensor arrays 805 are used to produce the data of display 1300, thedisplayed values can be an “average” of the values taken from a givenarray 805. This “average” can be calculated by the processor of thedisplay device 420.

Referring now to FIG. 14D, this Figure illustrates an exemplary display1302 of providing users with guidance for properly orienting a singlecompartment sensor 405 over a compartment of an animal, such as a humanleg, according to one exemplary embodiment of the invention. The display1302 can be generated by display device 420 so that a medicalpractitioner is provided with instructions and graphical information onhow to mount and operate the compartment sensors 405 of the system. Thedisplay may provide an illustration of the body part having thecompartment of interest. In the exemplary embodiment of FIG. 14D, thecompartment of interest is located within the lower human leg 100.

An illustration of the lower human leg 100 is provided in display 1302.On the body part having the compartment of interest, the display device420 can identify the longitudinal axis 450 by marking or flagging thisaxis 450 with a text box label 1309. The display 1302 can also identifyan illustration of the compartment sensor 405A by marking or flaggingthis illustration with another text box label 1311. The display 1302 canalso identify a general region for a compartment of interest byencapsulating the region with a geometric outline such as an ellipse andmarking this ellipse with another text box label 1307.

The display 1302 can also include a miniaturized view 1301 of across-section of the compartment of interest, similar to the viewsillustrated in FIGS. 9A and 9B for this exemplary embodiment that isassessing a lower leg compartment 905. The display 1302 may also allowthe user to expand the cross-sectional view 1301 of the compartment ofinterest by allowing the user to double-click or touch the actualdisplay of the cross-section. Multiple sections including an axial,coronal and/or sagittal view may be included in the on-screeninstructions for placement. Upon such action by the user, the displaydevice 420 may enlarge the cross-sectional view 1301 to a sizecomparable or equivalent to that illustrated in FIG. 9A. Once themedical practitioner has positioned the sensor 405 on the patient overthe desired compartment of interest, the display 1302 can be refreshedto include the next compartment of interest.

Referring now to FIG. 15A, this Figure illustrates a front view 1500 oflower limbs, such as two lower legs of a human body, that are beingmonitored by four compartment sensor arrays 805 according to anexemplary embodiment of the invention. The four sensor arrays 805 can bepositioned along compartments of interest by orienting the alignmentmechanism 410 along the longitudinal axis of a respective compartment.Multiple central scan depth markers 415 and numerical depths (notillustrated in FIG. 15A) can be positioned over each lightsource/receptor set of a sensor array 805 to locate where eachmeasurement is obtained for identifying sites of a hematoma, which willbe described in more detail in connection with FIGS. 15B-16 below.

Referring now to FIG. 15B, this Figure illustrates a display 1505 of thedisplay device 420 that can be used to monitor hematomas and/or bloodflow according to one exemplary embodiment of the invention. The display1505 can include an average oxygenation level 1515 of thirty-six at aninstant of time that is determined from the two compartment sensorarrays 805A1, 805B1 of a patient's right leg 100A which is injured inthis exemplary case. Meanwhile, the display 1505 can also include anaverage oxygenation level 1510 of fifty-three at the same instant oftime that is determined from the two compartment sensor arrays 805A2,805B2 of a patient's left leg 100B which is uninjured in this exemplarycase.

The display 1505 can also provide oxygenation values that it isreceiving from each of the individual sensors 405 in a first sensorarray 805 not illustrated. For the injured right leg 100A illustrated inthe display, the oxygenation levels vary between thirty-two andforty-four. However, in the exemplary embodiment illustrated in FIG.15B, there are three individual sensors 405 (not illustrated in thisFigure) of the sensor array 805A1 that are not producing any oxygenationvalues which have been provided with the letter “H” to denote a possiblehematoma. For the uninjured leg 100B, the individual compartment sensors405 (not illustrated) of the two sensor arrays 805A2, 805B2 haveprovided oxygenation levels that range between 50 and 54 which arebelieved to be in the normal range for normal blood flow. Also, Whileindividual sensors 405 that are not illustrated here (such as thosedescribed in connection with FIG. 4A above), one of ordinary skillrecognizes that such individual compartment sensors 405 can besubstituted anywhere were the compartment array sensors 805 are shown.

Referring now to FIG. 16, this Figure illustrates a display 1600 of thedisplay device 420 for an instant of time after the display of FIG. 15Band which can be used to monitor hematomas and/or blood flow accordingto one exemplary embodiment of the invention. The display 1600illustrates that the hematoma or absence of healthy blood flow conditionbeing tracked by sensor arrays 805A1, 805B1 (of FIG. 15A) is expanding.The display 1600 can include a warning message 1605 such as“WARNING—HEMATOMA EXPANDING!” to alert the medical practitioner of thechanging conditions of the compartments 905 of interest in the injuredor traumatized area. In FIG. 16, the average oxygenation level 1510 ofthe injured leg 100A decreased in value from thirty-six to twenty-four.Further, the number of individual sensors 405 (not illustrated butvalues shown) detecting a hematoma or lack of healthy blood flowcondition increased from two sensors detecting the condition in FIG. 15Bto seven sensors detecting the condition in FIG. 16 as indicated by the“H” values on display 1505. Meanwhile, the average oxygenation level1515 of the uninjured left leg 100B changed slightly from fifty-three tofifty-two.

With the display 1600 that provides the compartment sensors 405 with “H”values in combination with the central scan depth markers 415 providedon the sensor arrays 805, the medical practitioner can easily locate thephysical sites on the leg 100 that contain the hematoma or lack ofhealthy blood flow. These positions can also be used by the medicalpractitioner to locate appropriate amputation level for diabetics orperipheral vascular disease, since peripheral vascular disease istypically worse distally (closer to the toes) and gradually improvescloser to the knee. The compartment sensor 405 or more specifically thearray system 805 can be used to aid a clinician or surgeon indetermining the level of amputation for peripheral vascular disease andor diabetes mellitus. By obtaining multiple readings at different levelsfrom the knee to the ankle, the surgeon can determine the appropriatelevel for amputation. The level of amputation is important since if thetissue is not well perfused, the surgical wound will not heal andrequire revision surgery and more of the patient's leg must be removed.

Referring now to FIG. 17, this Figure illustrates a sensor design formeasuring the optical density of skin according to one exemplaryembodiment of the invention. The depth of tissue measurement using NIRSis based on separation of the optical transmitter 510 and the opticalreceiver (see FIGS. 18A-B). In order to obtain readings of only the skin(very shallow depths), the separation between the optical transmitter510 and optical receiver 515 would have to be very small and which maynot be feasible. In this exemplary embodiment, the sensor 405 cancomprise a material 1705 of known optical density that can be positionedbetween the substrate 530 and the skin 1710. In this way, the light meanpaths 710A, 710B will only penetrate upper layers of the leg 100, suchas the skin layers 1710. The thickness of the known material 1705 can bevaried to adjust for different desired scan depths made by the lightmean paths 710A, 710B. Since the optical density of the material 1705 isknown, then any near infrared light absorption will be attributable tothe layers of tissue of interest. And in this case, the optical densityof the skin 1710 can be determined. According to a further exemplaryembodiment, one of the photoreceptors 702A, 702B can be removed from theoptical receiver 515 in order to decrease the depth of the scan. Forexample, if the second photoreceptor 702A was removed, the depth of thescan would only extend as deep as the light mean path 710B for thephotoreceptor 702B.

The inventor has recognized that skin pigmentation can affect theoxygenation values of a patient that uses near-infrared compartmentsensors 405. This effect on oxygenation levels is also acknowledged inthe art. See an article published by Wassenar et al. in 2005 onnear-infrared system (NIRS) values. As with solar light, skinpigmentation caused by the biochemical melanin is a major factor inlight absorption. In the inventor's research, skin pigmentation has beendemonstrated to be a significant factor in measuring oxygenation levelsamong patients. The inventor has discovered that there was approximatelya ten point difference when comparing low pigmentation subjects(Caucasians, Hispanics & Asians) with higher pigmented subjects (AfricanAmerican). The pigmented subjects had average scores of approximatelyten points lower when compared to non-pigmented subjects. See Table 1below that lists data on the difference between measured oxygenationlevels of uninjured patients due to skin pigmentation.

TABLE #1 Difference in measured oxygenation levels between White andDark Pigmentation Skinned Subjects Avg White Dark Diff p value Anterior60 51 9 <0.0001 Lateral 61 52 9 <0.0001 Deep 66 53 13 <0.0001 Post Sup66 52 14 <0.0001 Post N = 10 (White) and 17 (Dark) (This study compared10 white subjects to 17 darker pigmented subjects) Statistics used a nonpaired, two tail student t-test for p-values P values show verystatistically significant differences between white (Caucasian, Asian &Hispanic) vs. Dark (African American) subjects

The p-value can be described as the chance that these findings were dueto chance alone. In all four compartments, the chance of finding thedifference (9-14) in average value between the two groups (dark andwhite) was less than 0.01% or less than 1 out of 10,000. In other wordsthe likelihood of these findings occurring by chance alone is veryunlikely. By convention, statistically significant findings areconsidered to be less than 5% or a p-value of <0.05 in comparison. SeeAPPENDIX A for the raw data that supports this data.

Conventional studies (Wassenar et al., 2005 and Kim et al., 2000) haveshowed that when subjects increase their activity, dark pigmented peopletend to have higher rates of loss of signal.

There have been no attempts as of this writing to account for skinpigmentation, or optical density, in oxygenation levels detected withsensors like the compartment sensor 405 discussed above. Therefore, thedesign illustrated in FIGS. 17-18 have been developed by the inventor toaccount for pigmentation optical density. With the embodiments of FIGS.17-18, skin pigmentation influences can be calibrated and accounted forwhen measuring oxygenation levels with sensors 405 that use nearinfrared light absorption principles. In this way, true or more accurateoxygenation levels of subcutaneous tissue such as muscle, cerebralmatter or organ tissue may be obtained. This calibration or pigmentationaccounting would also allow for comparison of values between differentpatients, since each individual will likely have different skinpigmentation values.

Referring now to FIG. 18A, this Figure illustrates a sensor 405 that canpenetrate two layers of skin 1805A, 1805B to obtain optical densityvalues according to one exemplary embodiment of the invention. Thedistance D1 between the optical transmitter 510 and optical receiver 515can be predetermined based on the scan depth 620A that is desired.

Referring now to FIG. 18B, this Figure illustrates a sensor 405 that canpenetrate one layer of skin 1805A according to one exemplary embodimentof the invention. This figure demonstrates how the depth of measurementfor oxygenation levels using the sensors 405 that operate according tonear infrared light absorption principles is usually directlyproportional to the optical transmitter and optical receiver separationdistance D. In FIG. 18B, the separation distance D2 is smaller than thatof the separation distance D1 of FIG. 18A. Accordingly, the central scandepth 620B of FIG. 18B is also shorter than the central scan depth 620Aof FIG. 18A.

According to one exemplary embodiment of the invention, the separationD1 and D2 between the optical transmitter 510 and optical receiver 515can range between approximately five millimeters to two centimeters.This separation distance D can be optimized to obtain an accuratereading of only the skin in the particular area of interest. One ofordinary skill in the art recognizes that skin is not a constant depthor thickness throughout a human body. Therefore, the depth 620 of thescan of a sensor 405 for which it is designed (ie. the leg forcompartment syndromes) may preferably be designed to vary to obtain anaccurate optical density value for skin in that specific body location.

Referring now to FIG. 18C, this figure illustrates a modifiedcompartment monitoring system 1800 that can correlate skin pigmentationvalues with skin optical density values in order to provide offsetvalues for oxygenation levels (derived from near infrared lightabsorption principles) across different subjects who have different skinpigmentation according to one exemplary embodiment of the invention. Thesystem 1800 can comprise a central processing unit of the display device420 or any general purpose computer. The CPU of the display device 420can be coupled to a compartment sensor 405′ that has been modified toinclude a skin pigment sensor 1820.

The skin pigment sensor 1820 may be provided with a known reflectanceand that can be used to calibrate the compartment sensor 405′ based onrelative reflectance of skin pigment which can affect data generatedfrom oxygenation scans. For example, the skin sensor 1820 can comprise anarrow-band simple reflectance device, a tristimulus colorimetricdevice, or scanning reflectance spectrophotometer. Conventional skinsensors available as of this writing include mexameter-18(CK-electronic, Koln, Germany), chromameters, and DermaSpectrometers.Other devices appropriate and well suited for the skin sensor 1820 arefound in U.S. Pat. No. 6,070,092 issued in the name of Kazama et al;U.S. Pat. No. 6,308,088 issued in the name of MacFarlane et al; and U.S.Pat. No. 7,221,970 issued in the name of Parker, the entire contents ofthese patents are hereby incorporated by reference.

The skin sensor 1820 can determine a standardized value for skinpigmentation of a patient by evaluating the melanin and hemoglobin inthe patient's skin. Once the skin melanin or pigment value is determinedit can be correlated to its calculated absorption or reflectance(effect) on the oxygenation levels using a predetermined calibrationsystem, such as the skin pigment table 1825 illustrated in FIG. 18C.From the skin pigment table 1825, the CPU 420 can identify or calculatean oxygenation offset value that can be incorporated in tissuehemoglobin concentration calculations for deep tissue oxygenation scans.Accounting for skin pigmentation will usually allow for information orvalues to be compared across different subjects with different skinpigmentation as well as using the number as an absolute value instead ofmonitoring simple changes in value over time.

Referring now to FIG. 19, this figure is a functional block diagram ofthe major components of a compartment monitoring system 1900 that canmonitor a relationship between blood pressure and oxygenation valuesaccording to one exemplary embodiment of the invention. The compartmentmonitoring system 1900 can include a CPU 420A of a display device 420Bthat is coupled to compartment sensors 405, a blood pressure probe 440,and a blood pressure monitor 445. The CPU 420A may also be coupled to avoice synthesizer 1905 and a speaker 1907 for providing statusinformation and alarms to a medical practitioner.

The CPU 420A can receive data from the blood pressure monitor 445 inorder to correlate oxygenation levels with blood pressure. The CPU 420Acan activate an alarm, such as an audible or visual alarm (or both) withthe voice synthesizer 1905 and speaker or displaying a warning messageon the display device 420B when the diastolic pressure of a patientdrops. It has been discovered by the inventor that perfusion can besignificantly lowered or stopped at low diastolic pressures and whencompartment pressures are greater than the diastolic pressure. Accordingto one exemplary embodiment, in addition to activating an alarm, the CPU420A of the compartment monitoring system 1900 can increase a frequencyof data collection for oxygenation levels and/or blood pressure readingswhen a low blood pressure condition is detected by the system 1900.

Referring now to FIG. 20, this figure is an exemplary display 2005 thatcan be provided on the display device 420 and which provides currentblood pressure values 2020 and oxygenation levels 2025 of a compartmentof interest according to one exemplary embodiment of the invention.Display 2005 can be accessed by activation of the mode switch 1305 ofFIG. 14.

In addition to displaying current blood pressure values 2020 andoxygenation levels 2025, the display 2005 can further include graphsthat plot a blood pressure curve 2035 and an oxygenation level curve2040. The blood pressure curve 2035 can represent blood pressure datataken over time that is plotted against the time axis 2030 (X-axis) andthe blood pressure axis 2010 (first Y-axis values). The oxygenationlevel curve 2040 can represent oxygenation levels taken over time thatis plotted against the time axis 2030 (X-axis) and the oxygenation levelaxis 2015 (second Y-axis values).

In this way, the relationship between blood pressure and potentialcompartment pressure based on the oxygenation levels can be directlytracked and monitored by a medical practitioner. As noted above, it hasbeen discovered by the inventor that perfusion can be significantlylowered or stopped at low diastolic pressures and when compartmentpressures are greater than the diastolic pressure. So when the bloodpressure of a patient starts to drop and if the oxygenation levels of acompartment being tracked also start to drop, the CPU 420A can sound anaudible alarm and display a warning message 2035 to the medicalpractitioner to alert him or her of this changing condition. Thiscorrelation between hemoglobin concentration (oxygenation levels) anddiastolic pressure can be used to estimate intra-compartmental pressureswithout having to use invasive, conventional needle measurements.

Additionally, a running average of oxygenation values over a certaintime period can be calculated and displayed. The time period could bealtered between multiple time periods from seconds to minutes to evenhours. The purpose of the running average would be to limit the amountof variability of the oxygenation values displayed on the screen. Thecurrent instantaneous value that is displayed in existing models is verylabile. By using a running average, the trends can be monitored and theinstantaneous changes can be smoothed out. This ability to decreasevolatility would be important to prevent continual alert triggering ifan alarm value was set by the medical practitioner.

In addition, with blood pressure input as described above, thediastolic, systolic and/or mean arterial pressure (MAP) can be displayed(not illustrated) against time on the same graph. Using the two dataseries of oxygenation and diastolic blood pressure, an estimate ofperfusion pressure (diastolic pressure minus intra-compartmentalpressure) can also be estimated by the CPU 420A.

Referring now to FIG. 21, this figure is a functional block diagram thatillustrates material options for a compartment sensor 405 according toone exemplary embodiment of the invention. Functional block 2105indicates that the structure of the compartment sensor can be made withsterile materials. For example, the substrate 530 (not illustrated) ofthe sensor 405 may be made of anyone or combination of the followingmaterials: various polymers such as the polyurethanes, polyethylenes,polyesters, and polyethers or the like may be used. Alternatively, eachcompartment sensor can be made with a sterile coating 2110 thatencapsulates the compartment sensor 405. The sterile coating can beapplied during manufacturing of the sensor 405 or it can be appliedafter manufacturing and provided as a container or sealable volume.Additionally, once the unit is constructed and finished, the device canbe sterilized using one or more off multiple processes including but notlimited to chemical, heat, gas or irradiation sterilization.

Referring now to FIG. 22, this figure illustrates an exemplary clinicalenvironment of a compartment sensor 405 where the sensor 405 can bepositioned within or between a dressing 2205 and the skin 1805 of apatient according to one exemplary embodiment of the invention. Sincethe inventive compartment sensor 405 can be made with or enclosed bysterile materials as noted in FIG. 21 above, the compartment sensor 405or an sensor array 805 can be positioned between a dressing 2205 and askin layer 1805 of a patient intra-operatively. In this way, a medicalpractitioner can monitor a compartment 905 of interest without the needto remove the dressing 2205 or adjust the position of the compartmentsensor 405.

Case Studies Using Compartment Sensors 405 and Conventional PressureMeasuring Methods

Case I

In 2007, a 44 year old Caucasian male fell 20 feet sustaining anisolated closed proximal tibia fracture with extension into the knee.Initial treatment included external fixation for stabilization on theday of injury. During surgery the compartments were firm butcompressible. At post operative check revealed that the compartmentswere more firm. There was mild pain with passive stretch, though thepatient was diffusely painful throughout both lower extremities.Intra-compartmental pressures were measured for all four compartmentsusing a conventional needle method with a Striker device (StrykerSurgical, Kalamazoo, Mich.). The anterior and lateral pressures measured50 mm Hg and the superficial and deep posterior compartments were 48 mmHg. The diastolic pressure was 90 mm Hg resulting in a 40 mm Hgperfusion pressure.

Tissue oxygenation (StO.sub.2) or oxygenation levels were evaluatedusing two compartment sensors 405. The oxygenation levels wereapproximately 80% in all four compartments. The compartment sensors 405were placed on the lateral and deep posterior compartments for continualmonitoring, which maintained oxygenation values near 80%. Higherpercentage oxygenation levels indicate more perfusion and higheroxy-hemoglobin concentrations.

All clinical decisions were based of the clinical symptoms and pressuremeasurements and not on the oxygenation levels. Two hours passed andcompartment pressures were repeated. The anterior and lateralcompartments remained at 50 mm Hg. The superficial and deep posteriorcompartments rose to 50 mm Hg as well. The patient's diastolic pressureremained at 90 mm Hg maintaining 40 mm Hg of perfusion pressure. Theoxygenation values remained near 80% for both the lateral and deepposterior compartments. Clinical symptoms were monitored closelythroughout the night.

Approximately 24 hours after the initial injury, the patient became moresymptomatic and began requiring more pain medication.Intra-compartmental measurements were repeated. The anterior and lateralcompartments remained at 51 mm Hg. The superficial and deep posteriorcompartments measured 61 mm Hg and 63 mm Hg respectively. However, thediastolic pressure dropped to 74 mm Hg decreasing the perfusion pressureto 11 mm Hg. Based on the pressure measurements and clinical symptoms,the patient underwent fasciotomy and was found to have no gross evidenceof muscle necrosis or neuromuscular sequelae at late follow up.

Throughout the monitoring period, the lateral compartment maintained anoxygenation level of approximately 80%. The oxygenation levels in thedeep posterior compartment began in the eighties and started to dropapproximately three hours after the second compartment pressuremeasurement. At time of fasciotomy, the oxygenation level for the deepposterior compartment was 58%. The gradual decline in muscle oxygenationmirrored the decrease in perfusion pressure over an extended period oftime.

This first case suggests that the compartment sensors 405 can be used tocontinually monitor an injured extremity. Initially, the patient hadelevated intra-compartmental pressures, but the perfusion pressure wasgreater than 30 mm Hg. The ensuing increase in clinical symptoms anddecrease in perfusion pressure correlated with the gradual decrease inoxygenation levels. Impaired perfusion was reflected in a decline in theoxygenation levels. These results are consistent with a previous studyby Garr et al. who showed a strong correlation between oxygenationlevels and perfusion pressures in a pig model. This case alsodemonstrates the ability of compartment sensors 405 to differentiatebetween compartments in the leg since the oxygenation levels in thelateral compartment remained elevated while the deep posterior valuesdeclined.

Case II

Also in 2007, a 32 year old Hispanic male sustained an isolated, closedSchatzker VI tibial plateau fracture after falling from a scaffold. Oninitial evaluation, the patient had tight compartments, but there wereno clinical symptoms of compartment syndrome. Active and passive rangeof motion resulted in no significant pain. Based on the concerns for thetense leg, intra-compartmental pressure measurements were obtained usinga Stryker device.

All compartments were greater than 110 mm Hg. The patient's bloodpressure was 170/112 mm Hg. The decision to perform a four compartmentfasciotomy was made. The compartment sensors 405 were placed on the deepposterior compartment as well as the lateral compartment for continualmonitoring. The lateral compartment was unable to give a consistentreading due to hematoma interference. The initial reading for the deepposterior was an oxygenation level of 65%. The deep posterior tissueoxygenation level steadily declined from 65% to 55% over the hour ofpreoperative preparation.

Upon intubation, a sharp drop in the oxygenation levels from 55% to 43%was observed. The anesthesia record showed a concomitant drop in bloodpressure at the time of induction from 171/120 mm Hg to 90/51 mm Hg. Thepatient underwent an uneventful fasciotomy and external fixation. Tissueexamination showed no gross signs of muscle necrosis and at nine monthsfollow-up there were no signs of sequelea. The oxygenation levelmonitoring of the compartment was acutely responsive and showed realtime changes to a decline in perfusion pressure in an injured extremity.

The responsiveness of the compartment sensors 405 to intra-compartmentalperfusion pressure is demonstrated by this second case study. Thispatient was initially asymptomatic even though his compartments wereover 110 mm Hg in all compartments. The oxygenation levels from thecompartment sensors 405 were able to detect gradual perfusion declinesover the hour prior to fasciotomy. Prior to induction of anesthesia, thepatient was able to maintain some tissue oxygenation by maintaining ahigh diastolic blood pressure. Once the patient was anesthetized duringintubation, the diastolic pressure was significantly reduced. Theoxygenation levels of the compartments dropped within thirty seconds ofinduction because the slight perfusion gradient was completely abolishedby the induced hypotension.

Case III

In 2007, a 62 year old Asian male suffered a closed midshaft tibiafracture in a motor vehicle crash. The patient was unresponsive andhypotensive at the scene of the accident and intubated prior to arrival.Upon presentation, the patient was hypotensive with a blood pressure of90/55 mm Hg. The injured leg was clinically tight on examination.

Oxygenation levels were measured for all four compartments. Theoxygenation levels were approximately at 50% for the anterior andlateral compartments while the two posterior compartments wereapproximately at 80%. The compartment sensors 405 were placed on theanterior and superficial posterior compartments for continuedmonitoring. Intra-compartmental pressures were measured at 50 mm Hg and52 mm Hg in the anterior and lateral compartments respectively using theconventional Striker device (needle pressure measuring method). Thesuperficial and deep compartment pressures were 19 mm Hg and 20 mm Hgrespectively. After the patient was stabilized by the trauma team, heunderwent fasciotomy. There were no gross signs of muscle necrosis andno complications at 7 months follow-up. Muscle oxygenation was able todifferentiate between compartments with hypoperfusion and adequateperfusion in a hypotensive and intubated patient.

This third case is evidence that the compartment sensors 405 are usefulin assessing established or existing compartment syndromes. Thecompartment sensors 405 can provide useful information in patients thatare unable to give feedback during a clinical examination such as thispatient who was intubated and hypotensive upon examination. Thesefindings correlate with the findings by Arbabi et al. who demonstratedoxygenation levels to be responsive in hypotensive and hypoxic pigs in alaboratory setting. The compartment sensors 405 can distinguish betweendifferent compartments and their respective perfusions. Clinically, inthis case, the whole leg was tense, but intra-compartmental pressureswere only elevated in the anterior and lateral compartments. Theoxygenation levels measured by the compartment sensors 405 wereproportional to the perfusion pressure with low values in the anteriorand lateral compartments, but elevated values in the two posteriorcompartments.

Conclusion for Three Case Studies:

These three cases suggest that compartment sensors 405 are responsiveand proportional to perfusion pressures within the injured extremity.These findings support previous studies documenting the importance ofperfusion pressure and not an absolute value in the diagnosis ofcompartment syndrome. The compartment sensors can distinguish betweencompartments and is useful in the unresponsive, intubated andhypotensive patient. Lastly, the compartment sensors 404 have thepotential to offer a continual, noninvasive and real time monitoringsystem that is sensitive in the early compartment syndrome setting. Inall three cases, a difference in oxygenation levels was demonstratedprior to any irreversible tissue injury.

Case IV

A 60 year old Middle Eastern male was shot in the right thigh. Initiallythe thigh was swollen but the patient was comfortable. Afterapproximately 12 hours after the initial injury the patient began tocomplain of increasing pain and required more pain medication. The thighwas more tense upon clinical exam. The patient was taken to the OR forfracture fixation and potential fasciotomy of the thigh.

NIRS sensors were placed on the anterior, posterior and medial(adductors) compartments of the thigh. Values for the injured side weresimilar or decrease when compared to the uninjured side. As previouslydescribed, injured tissue should show increased values due to hyperemia.The injured side anterior, posterior and medial values were 54, 53 and63 respectively. The uninjured values for the anterior, posterior andmedial were 51, 55 and 63 respectively.

The compartment pressures were measured in all three compartments. Theintra-compartmental pressures for the anterior, posterior and adductorswere 44, 59 and 30 respectively. Once the patient was induced foranesthesia and the patient's blood pressure dropped from 159/90 to90/61, the patients NIRS values dropped within in 30 seconds of the hisblood pressure drop. Once the blood pressure was dropped and theperfusion pressure was eliminated, the new values for the anterior,posterior and medial compartments were 29, 40 and 35.

Study: Sphygmomanometer Model & Invention's Sensitivity & Responsiveness

A study was conducted to determine the sensitivity and responsiveness ofthe inventive compartment monitoring system 400. Specifically, thepurpose of the study was to evaluate the invention over the anteriorcompartment with a cuff around the thigh at different pressures(simulating a compartment Syndrome) to show responsiveness to increasingpressures in the leg.

The inventor's hypothesis was that the inventive compartment monitoringsystem 400 will show normal oxygenation at levels below pressuresequivalent to compartment syndrome. Once pressures become equal to thediastolic blood pressure, it was believed the inventive system 400 wouldshow significant deoxygenation because the capillary perfusion pressurewill be passed. Continued monitoring will be obtained until a plateau ornadir is obtained.

Materials & Methods:

Thigh Cuff Pressures: 0 mmHg: Baseline; Increase cuff by 10 mmHg andhold for 10 minutes; At the end of each ten minute period blood pressureand NIRS values were obtained; Repeat incremental increases until obtaindecreased oxygenation level readings; and Observe post release response& time to return to baseline

Outcomes:

It was confirmed that the compartment monitoring system 400 is sensitiveto changing pressures. A correlation with decreased perfusion wasdiscovered once the pressure approaches diastolic pressure. Theinventive system 400 does not reflect complete vascular compromise untiltourniquet pressure supersedes systolic blood pressure because of venouscongestion. These findings are consistent with previously describedstudies.

Statistical Analysis:

A significant difference is observed once tourniquet pressure equals thediastolic pressure (Perfusion pressure of zero). The venous congestionphenomenon which has been described with the tourniquet model forcompartment syndromes maintains some flow until cuff pressure is raisedto above systolic pressure (no flow). Venous congestion is thephenomenon when the higher systolic blood pressure is able to overcomethe tourniquet pressure applied to the leg during that burst of pressurecreated by the heart's contraction when the tourniquet compression isabove diastolic pressure but below systolic pressure.

Referring now to FIG. 23, this figure is a graph 2300 of perfusionpressure plotted against oxygenation levels (O.sub.2) of the studyconducted to determine the sensitivity and responsiveness of theinventive compartment monitoring system 400. The section between pointsA and B show the combined points of all subjects studied during thestudy when the tourniquet pressure was below the diastolic pressure. Asshown in the graph, the grouping is mostly flat and does not show anydecrease as the tourniquet pressure is increased. After point B betweenpoint B and C, the tourniquet pressure is above the diastolic pressureand the perfusion pressure becomes zero or negative. During this sectionof the graph, there is a significant drop in muscle oxygenation. Thedata points in FIG. 23 use the actual compartment monitoring values,which as described above, can vary based on skin pigmentation.Therefore, there is a wider range of values in oxygenation numbers and awider spread of data points. See APPENDIX B for the raw data thatsupports this graph 2300.

Referring now to FIG. 24, this figure is a graph 2400 of perfusionpressure plotted against a change in the oxygenation levels (O.sub.2)from a baseline for each subject of the study conducted to determine thesensitivity and responsiveness of the inventive compartment monitoringsystem 400.

In the FIG. 24, the change from baseline was used instead of theabsolute number presented by the compartment sensor. The effects ofpigment were removed when change from baseline values was used. Baselinewas defined as the value before the tourniquet was placed. The spreadbetween data points is much less. As shown again between points A and B,there is a very small and gradual decrease in tissue oxygenation untilpoint B (moving from high perfusion pressures to lower perfusionpressures or from right to left). Once the perfusion pressure, becomeszero or negative, the change from baseline was much larger and morerapid. Both graphs show how the tissue oxygenation is highly sensitiveto perfusion pressure and the critical point is when the perfusionpressure changes from positive to negative. As described above, thediagnosis of compartment syndrome is based on the perfusion pressure(diastolic pressure minus compartment pressure). Therefore, thecompartment monitoring system 400 has the capability to show real-timechanges in perfusion prior to any irreversible tissue damage. SeeAPPENDIX B for the raw data that supports this graph 2300.

This study supports the theory that oxygenation levels measure with thecompartment sensors 405 decrease as perfusion pressure also decreases(Perfusion pressure=diastolic-cuff pressure). The study also indicatesthat there are no significant changes in measured oxygenation levelsuntil there is increase above the diastolic pressure. The findings ofthis study as illustrated in FIGS. 23 and 24 correlate with previousstudies using other determinants of flow (Xenon clearance; Clayton,1977; Dahn, 1967; Heppenstall, 1986; Matava, 1994).

Study of Established Acute Compartment Syndromes:

Based on the clinical evaluation in established acute compartmentsyndrome patients the diagnosis of compartment syndrome was made. Itspurpose was to evaluate the ability of the inventive compartmentmonitoring system 400 to detect hypoperfusion in the differentcompartments of the lower leg. This evaluation was made to demonstratethe invention's sensitivity to increased pressures versus uninjuredlegs.

Hypothesis:

There will be a significant difference between the injured and uninjuredvalues of the compartment monitoring system 400. There will also be aninverse relationship between compartment pressures and measuredoxygenation levels by the sensors 405. In other words, the oxygenationvalues would be directly proportional to perfusion pressures.

Material & Methods:

Oxygenation levels and pressure measurements for each compartment inestablished compartment syndromes were obtained. Readings for both legswere compared for each compartment.

Unknowns:

How will thick subcutaneous fat affect the compartment sensors 405?

What values will we obtain for the posterior compartments?

Preliminary Results:

Hyperemia (increased oxygenation levels) for fractures without anycompartment syndrome symptoms has been demonstrated by the inventorsstudies (Table #3 and #4). In early compartment syndromes, theoxygenation values were equal between the two different legs. Once thecompartment syndrome became advanced, and the perfusion pressure wasdecreased or eliminated, the oxygenation values in the injured legdropped below the uninjured leg. There was some difficulty in obtainingoxygenation levels over a hematoma. Therefore, when oxygenation valuesbetween the two legs become equal, there should be concern for acompartment syndrome and fasciotomy should be considered. Once theinjured levels drop below the uninjured leg, a fasciotomy should beperformed.

Oxygenation levels are extremely responsive to changes in perfusion inregards to pressure changes. Compartment sensors 405 can differentiatebetween compartments. Oxygenation levels can work and are accurate inintubated patients. Oxygenation levels do respond over extended timeperiods and over very short periods of time and rapid changes inintra-compartmental pressures.

Oxygenation levels and hyperemia are maintained at least two to threedays post injury or surgery. Post-operative values are also high in theoperated on leg—.about.69-72 (Standard deviation of 9-12) with anaverage difference of 15-17%. The compartment sensors 405 work as anoninvasive tool. Oxygenation levels can be monitored by sensors 405over extended periods of time. Compartment sensors 405 do respond tochanges in perfusion both gradual and sudden. The sensors 405 candifferentiate between different compartments.

TABLE #2 Comparison of Oxygenation Levels between Injured Limb andNon-injured Limb Avg Injured Uninjured Diff p value Anterior 46 54 −60.07 Lateral 45 54 −9 0.01 Deep 54 68 −14 0.05 Post Sup 50 60 −10 0.04Post Significant difference using one tailed, paired student t-test wasused for statistical analysis.

In three out of four compartments, the p-value showed statisticalsignificance (p-value<0.05). The one compartment that was not less than0.05, the anterior compartment, the p-value was 0.07 which is very closeto 0.05. As described below, the normal situation should be theopposite. The injured side should be and is shown to be significantlyhigher when compared to the uninjured side. The p-value can be describedas the chance that these findings were due to chance alone. Byconvention, statistically significant findings are considered to be lessthan 5% or a p-value of <0.05 in comparison. This means that there is a5% chance that these findings are due to chance alone and that there isno difference between the two groups. See APPENDIX A for the raw datathat supports this data.

Study of Fracture Hyperemia with Inventive Compartment Monitoring System400

A study of fracture hyperemia with the inventive compartment monitoringsystem 400 was made. The purpose of this study was to examine noncompartment syndrome patients with fractures of the lower leg.

Hypothesis:

The injured leg will show a hyperemic response to injury and haveelevated blood flow causing an increase in oxygenation values.

Materials & Methods:

Compare uninjured leg to injured leg to see if there is a statisticaland reproducible increase at time of injury. The data is important todescribe normal fracture response to compare with compartment syndromeresponse.

Results:

Patients have approximately 15 pts higher on the injured side comparedto the uninjured side. Time of measurement was approximately 16 hourspost injury (range 2, 52).

TABLE #3 Oxygenation Values for Injured versus Uninjured Lower LegMeasurements. Avg Injured Uninjured Diff p value Anterior 69 55 14<0.0001 Lateral 70 55 15 <0.0001 Deep 74 57 17 <0.0001 Post Sup 70 56 14<0.0001 Post N = 26 (there were 26 subjects examined in this study.)Statistical Analysis Calculated p-Values Using a Two Tailed, PairedStudent t-Test.

In normal lower leg fracture situations without vascular injury orcompartment syndrome, comparison between injured and uninjured legs showthat the injured leg should be significantly higher with and averageelevation of between 14 and 17 points. This finding is consistent withthe hyperemia associated with injury. This effect is a long lastingeffect that lasts over 48 hours after injury and surgery as seen bythese results. The p-value can be described as the chance that thesefindings were due to chance alone. In all four compartments, the chanceof finding the difference (14-17) in average value between the twogroups (injured and uninjured) was less than 0.01% or less than 1 out of10,000. In other words the likelihood of these findings occurring bychance alone is very unlikely. By convention, statistically significantfindings are considered to be less than 5% or a p-value of <0.05 incomparison. See APPENDIX A for the raw data that supports this data.

TABLE #4 Oxygenation Values for Injured versus Uninjured Lower LegMeasurements 2 Days After Surgery. Avg Injured Uninjured Diff p valueAnterior 71 55 16 <0.0001 Lateral 70 54 16 <0.0001 Deep 73 58 15 <0.0001Post Sup 73 56 17 <0.0001 Post N = 17 (This study included 17 patients)Average time of measurement was 71 hours after injury and 44 hours afteroperation

The p-value can be described as the chance that these findings were dueto chance alone. In all four compartments, the chance of finding thedifference (15-17) in average value between the two groups (injured anduninjured) was less than 0.01% or less than 1 out of 10,000. In otherwords the likelihood of these findings occurring by chance alone is veryunlikely. By convention, statistically significant findings areconsidered to be less than 5% or a p-value of <0.05 in comparison. SeeAPPENDIX A for the raw data that supports this data.

TABLE #5 Uninjured Controls Comparing Right and Left Leg Differences.Avg Avg Right Left Diff Val Anterior 55 54 1 55 Lateral 56 54 2 56 Deep60 58 2 59 Post Sup 59 58 1 58 Post N = to 25 (There were 25 patientsincluded in this study.) No difference was found between right and leftsides.

These findings are important for two different reasons. First, thedifference between the two legs was very small (on average between 1 or2 points). Therefore, the other findings that show significantdifferences between legs cannot be explained as normal variance.Uninjured patients have oxygenation values between the two legs that aretypically very similar (within 1-5 points of each other). Second, normaloxygenation values for uninjured subjects were in the high 50's. Thisvalue varied based on pigmentation of the skin as showed above. SeeAPPENDIX A for the raw data that supports this data.

Exemplary Method for Monitoring Oxygenation Levels of a Compartment

Referring now to FIG. 25, this figure is logic flow diagram illustratingan exemplary method 2500 for monitoring oxygenation levels of acompartment according to one exemplary embodiment of the invention. Theprocesses and operations of the inventive compartment monitoring system400 described below with respect to the logic flow diagram may includethe manipulation of signals by a processor and the maintenance of thesesignals within data structures resident in one or more memory storagedevices. For the purposes of this discussion, a process can be generallyconceived to be a sequence of computer-executed steps leading to adesired result.

These steps usually require physical manipulations of physicalquantities. Usually, though not necessarily, these quantities take theform of electrical, magnetic, or optical signals capable of beingstored, transferred, combined, compared, or otherwise manipulated. It isconvention for those skilled in the art to refer to representations ofthese signals as bits, bytes, words, information, elements, symbols,characters, numbers, points, data, entries, objects, images, files, orthe like. It should be kept in mind, however, that these and similarterms are associated with appropriate physical quantities for computeroperations, and that these terms are merely conventional labels appliedto physical quantities that exist within and during operation of thecomputer.

It should also be understood that manipulations within the computer areoften referred to in terms such as listing, creating, adding,calculating, comparing, moving, receiving, determining, configuring,identifying, populating, loading, performing, executing, storing etc.that are often associated with manual operations performed by a humanoperator. The operations described herein can be machine operationsperformed in conjunction with various input provided by a human operatoror user that interacts with the computer.

In addition, it should be understood that the programs, processes,methods, etc. described herein are not related or limited to anyparticular computer or apparatus. Rather, various types of generalpurpose machines may be used with the following process in accordancewith the teachings described herein.

The present invention may comprise a computer program or hardware or acombination thereof which embodies the functions described herein andillustrated in the appended flow charts. However, it should be apparentthat there could be many different ways of implementing the invention incomputer programming or hardware design, and the invention should not beconstrued as limited to any one set of computer program instructions.

Further, a skilled programmer would be able to write such a computerprogram or identify the appropriate hardware circuits to implement thedisclosed invention without difficulty based on the flow charts andassociated description in the application text, for example. Therefore,disclosure of a particular set of program code instructions or detailedhardware devices is not considered necessary for an adequateunderstanding of how to make and use the invention. The inventivefunctionality of the claimed computer implemented processes will beexplained in more detail in the following description.

Further, certain steps in the processes or process flow described in thelogic flow diagram must naturally precede others for the presentinvention to function as described. However, the present invention isnot limited to the order of the steps described if such order orsequence does not alter the functionality of the present invention. Thatis, it is recognized that some steps may be performed before, after, orin parallel other steps without departing from the scope and spirit ofthe present invention.

Referring again to FIG. 25, Step 2501 is the first step in the process2500 for monitoring oxygenation levels of a compartment according to oneexemplary embodiment of the invention. In step 2501, a compartmentsensor 405 may be manufactured from sterile materials as described abovein connection with FIG. 21. Alternatively, a compartment sensor 405 canbe encapsulated with sterile materials so that it can be used in asurgical environment or so that it can be place adjacent to wounds (orboth).

In step 2503, a central scan depth marker 415 can be provided on acompartment sensor 405. In step 2506, an alignment mechanism 410 canalso be provided on the compartment sensor 405 to allow a medicalpractitioner to orient a sensor 405 along a longitudinal axis of acompartment of interest.

In step 2509, an expansion device 535 may be provided between two ormore grouped compartment sensors 405 as illustrated in FIG. 5A. In step2512, the processor and display device 420 may receive input from a useron the type of compartment that is to be monitored by the inventivesystem 400.

In step 2515 and in response to the input of step 2512, the displaydevice 420 can display a location of the selected compartment ofinterest such as illustrated in FIG. 14D. The display device 420 canalso display the longitudinal axis 450 of the compartment of interest.Next, in step 2518, the display device 420 may display an ideal oroptimal position for the compartment sensor 405 along the longitudinalaxis of the compartment of interest as illustrated in FIG. 14D.

In step 2521, with the information from steps 2515-2518, the medicalpractitioner can identify a proper position of the compartment sensor ona patient through orienting the alignment mechanism 410 with thelongitudinal axis of the compartment and by using the central scan depthmarker 415.

In step 2527, the compartment sensor 405 can be placed on the patient.In step 2530, the compartment sensor can obtain a skin pigment value ofthe patient's skin through using a skin sensor 1820 as illustrated inFIG. 18C or thorough using a shallow sensor 405 as illustrated in FIG.17. In step 2533, the processor 420A can determine an oxygenation offsetvalue based on the skin pigment value obtained in step 2530.

Next, in step 2536, the offset value from step 2533 can be used duringoxygenation level monitoring. In step 2539, the blood pressure of thepatient can be monitored with a probe 440 and blood pressure monitor asillustrated in FIGS. 4 and 19. In step 2542, the system 400 can monitorthe oxygenation levels of one or more compartments of interest overtime. In step 2545, the system 400 can also monitor the oxygenationlevels of healthy compartments to obtain a baseline while monitoring thecompartments adjacent to an injury or trauma as illustrated in FIG. 15B.

In step 2547, the oxygenation levels of compartments of interest can bedisplayed on the display device 420 as illustrated in FIGS. 10, 14C,15B-C, 16, and 20. In step 2550, the blood pressure of the patient canalso be displayed on the display device as illustrated in FIG. 20. Instep 2553, the display device 420 and its processor can monitor therelationship between the blood pressure values and oxygenation levels asillustrated in FIG. 20.

In step 2556, the display device 420 can activate an alarm in the formof an audible or visual message (or both), when the oxygenation levelsdrop below a predetermined value or if a significant change in thelevels is detected as illustrated in FIG. 20. In step 2559, the displaydevice can also activate an alarm in the form of an audible or visualmessage (or both), when both the oxygenation levels and blood pressuredrop simultaneously or if one of them falls below a predeterminedthreshold value as described in connection with FIG. 20.

In step 2562, the display device 420 and its processor can increase afrequency of data collection for oxygenation levels and blood pressurevalues if both values drop. The exemplary process then ends.

Alternative Exemplary Embodiments

The inventive compartment monitoring system 400 could also be used forfree flap as well as tissue transfer monitoring. Currently skin colorand capillary refill are used to evaluate flap viability. This practicerequires repeated examinations and subjective criteria. The conventionalmethod requires leaving skin exposed or taking down dressings which canbe very labor intensive. As a solution to the conventional approach, asensor 405 can be sterilized and it can record average oxygenationlevels over time. The sensor 405 can be placed on the flap (free ortransferred).

The compartment sensor 405 can also be used to monitor oxygenation oftissue transferred for vascular patency. Specifically, for hand or anyupper extremity surgery, the compartment sensor can be used to monitorthe progress of revascularization of fingers, hands and arms based onmeasured oxygenation levels. The sensor 405 can be applied to theinjured extremity once vascular repair has been performed in order tocontinue monitoring of vascular repair. A baseline of a correspondinguninjured or healthy extremity can be made once repair to the injuredextremity is done—before closure—in order to get a baseline value whilelooking at the repair. Sensors 405 for this application will also needto be sterilized and be able to conduct scans with depths of at least0.5 centimeters.

It should be understood that the foregoing relates only to illustratethe embodiments of the invention, and that numerous changes may be madetherein without departing from the scope and spirit of the invention asdefined by the following claims.

Compartment Syndrome Patients Anterior Lateral Pt Injur Unin Diff ICP PPInjur Unin Diff ICP PP 1 66 58 8 78 −13 58 65 −7 79 −14 2 35 50 −15 170−70 41 49 −8 176 −76 3 15 41 −26 107 −37 15 40 −25 104 −34 4 46 44 2 724 34 49 −15 82 −6 5 45 47 −2 71 18 53 53 0 71 18 6 56 64 −6 59 −4 55 61−6 57 −2 7 8 58 66 −8 142 −44 51 64 −13 142 −44 9 50 51 −1 57 1 53 54 −155 Avg 46.4 52.6 −6 94.5 −18.1 45 54.4 −9.38 95.8 −19.4 Std D 15.8 9.1610.6 41.6 29.5 14.5 8.58 8.16 42.9 30.3 pVal 0.07 0.01 Rang 66,15 41,668,−26 15,58 40,65 0,−25 Deep Posterior Superficial Posterior Pt InjurUnin Diff ICP PP Injur Unin Diff ICP PP 1 76 −11 58 57 1 84 −19 2 116−16 43 67 −24 115 −15 3 104 −34 47 45 2 99 −29 4 57 19 32 56 −24 71 5 556 33 56 55 1 61 28 6 46 67 −21 63 −8 55 64 −9 62 −7 7 56 61 −5 61 10 6259 3 59 12 8 59 75 −16 135 −37 50 77 −27 110 −12 9 3 Avg 53.7 67.7 −1483.5 −5.5 50.4 60 −9.63 82.6 −4.63 Std D 6.81 7.02 8.19 30.6 24.7 9.649.49 13.3 22.8 18.5 pVal 0.05 0.04 Rang 46,59 61,75 −5,−21 32,62 45,773,−27

Initial Injury Study Non Compartment Syndrome Anterior Lateral Deep PostSup Posterior Pt Injured Uninjured Diff Injure d Uninjured Diff InjuredUninjured Diff Injured Uninjured Diff 1 70 65 5 70 58 12 77 68 9 2 64 5410 61 56 5 72 57 15 3 58 47 11 49 44 5 49 43 6 4 77 63 14 82 66 16 83 6122 79 66 13 5 82 58 24 78 59 19 72 63 9 73 56 17 6 62 54 8 61 53 8 66 4917 63 51 12 7 64 48 16 68 46 22 76 52 24 64 44 20 8 70 62 8 73 57 16 8059 21 87 64 23 9 62 47 15 71 53 18 74 52 22 66 53 13 10 73 60 13 75 5223 71 52 19 72 56 16 11 73 58 15 88 51 37 88 62 26 80 52 28 12 63 53 1061 50 11 72 57 15 73 61 12 13 78 73 5 82 75 7 86 70 16 81 71 10 14 67 5710 70 62 8 74 64 10 71 62 9 15 71 46 25 63 43 20 71 43 28 69 46 23 16 7747 30 66 55 11 66 54 12 62 57 5 17 55 46 9 62 48 14 62 51 11 63 45 18 1882 58 24 79 64 15 90 75 15 79 74 5 19 54 49 5 60 47 13 54 52 2 57 50 720 79 71 8 90 81 9 87 72 15 86 69 17 21 70 49 21 65 47 18 64 45 19 61 529 22 78 44 34 76 43 33 82 54 28 69 48 21 23 74 65 9 76 63 13 78 61 17 7365 8 24 68 53 15 66 56 10 77 58 19 70 55 15 25 62 51 11 68 53 15 60 51 960 50 10 26 68 53 15 66 56 10 77 58 19 70 55 15 Avg 69.3 55 14.2 70.255.3 14.9 74.3 57.2 17.2 70.2 56.5 13.7 Med 70 53.5 12 69 54 13.5 74 5717 70.5 55.5 13 Std D 7.93 7.94 7.75 9.47 9.27 7.69 9.48 8.14 6.5 8.998.72 6.03 pVal 0.000000 0.000000 0.000000 0.000000 Non CompartmentSyndrome 2 Days Post-Op Anterior Lateral Deep Post Sup Posterior PtInjured Uninjured Diff Injured Uninjured Diff Injured Uninjured DiffInjured Uninjured Diff 1 79 51 28 75 54 21 69 47 22 67 43 24 2 56 47 951 45 6 58 46 12 56 48 8 3 82 52 30 78 47 31 82 59 23 88 50 38 4 63 55 865 54 11 74 58 16 70 58 12 5 62 50 12 63 47 16 63 58 5 62 54 8 6 61 5011 62 54 8 68 60 8 81 55 26 7 69 61 8 71 64 7 79 69 10 75 68 7 8 68 4226 65 39 26 75 41 34 62 44 18 9 85 73 12 79 62 17 95 75 20 93 73 20 1071 62 9 72 58 14 66 61 5 74 61 13 11 83 70 13 82 67 15 87 71 16 88 72 1612 77 47 30 66 55 11 66 54 12 62 57 5 13 64 56 8 62 50 12 67 56 11 63 5112 14 70 49 21 80 55 25 73 63 10 65 54 11 15 84 64 20 90 63 27 88 64 2488 63 25 16 60 47 13 63 51 12 64 51 13 76 43 33 17 71 63 8 61 57 4 87 6225 63 60 3 Avg 70.9 55.2 15.6 69.7 54.2 15.5 74.2 58.5 15.6 72.5 56.116.4 Med 70 52 12 66 54 14 73 59 13 70 55 13 Std D 9.3 8.84 8.31 9.857.37 8 10.5 8.97 7.95 11.5 9.35 10 pVal 0.00000 0.00000 0.00000 0.00000

Uninjured Subjects (Normal NIRS Values) Anterior Lateral Deep Post SupPosterior Pt R L Diff AV R L Diff AV R L Diff AV R L Diff AV 1 50 46 4 446 48 −2 2 48 49 −1 1 40 40 0 0 2 58 56 2 2 60 60 0 0 63 60 3 3 64 57 77 3 49 47 2 2 48 50 −2 2 47 44 3 3 47 44 3 3 4 59 60 −1 1 60 57 3 3 5861 −3 3 58 61 −3 3 5 54 51 3 3 51 48 3 3 55 51 4 4 55 52 3 3 6 55 52 3 358 53 5 5 68 65 3 3 69 63 6 6 7 56 57 −1 1 52 58 −6 6 52 62 −10 10 64 67−3 3 8 54 57 −3 3 56 57 −1 1 61 61 0 0 55 60 −5 5 9 49 42 7 7 50 43 7 755 49 6 6 52 52 0 0 10 48 44 4 4 51 46 5 5 72 60 12 12 51 46 5 5 11 7165 6 6 73 68 5 5 75 76 −1 1 69 75 −6 6 12 48 50 −2 2 48 53 −5 5 49 54 −55 47 49 −2 2 13 45 50 −5 5 46 51 −5 5 47 46 1 1 54 53 1 1 14 59 51 8 860 52 8 8 59 55 4 4 61 57 4 4 15 48 56 −8 8 50 55 −5 5 56 58 −2 2 49 55−6 6 16 42 43 −1 1 44 43 1 1 43 42 1 1 46 37 9 9 17 54 56 −2 2 55 60 −55 64 60 4 4 67 62 5 5 18 54 54 0 0 51 47 4 4 52 54 −2 2 59 53 6 6 19 4243 −1 1 48 42 6 6 52 47 5 5 42 48 −6 6 20 68 65 3 3 70 67 3 3 73 68 5 574 71 3 3 21 62 61 1 1 61 55 6 6 68 67 1 1 68 70 −2 2 22 49 46 3 3 52 484 4 66 55 11 11 64 66 −2 2 23 67 62 5 5 70 65 5 5 88 81 7 7 77 70 7 7 2474 68 6 6 74 69 5 5 68 65 3 3 76 67 9 9 25 66 64 2 2 74 71 3 3 70 71 −11 71 66 5 5 Avg 55.2 53.8 1.4 3.32 56.3 54.6 1.68 4.16 60.4 58.4 1.923.92 59.2 57.6 1.52 4.32 T avg 54.5 55.5 59.4 58.4 Std D 8.81 7.73 3.832.29 9.4 8.5 4.35 1.95 10.9 9.83 4.74 3.21 10.8 10.2 4.81 2.48

White vs. Dark Pigmented Skin Comparison African American AnteriorLateral Deep Post Sup Posterior Pt R L Diff AV R L Diff AV R L Diff AV RL Diff AV 1 50 46 4 4 46 48 −2 2 48 49 −1 1 40 40 0 0 3 49 47 2 2 48 50−2 2 47 44 3 3 47 44 3 3 7 56 57 −1 1 52 58 −6 6 52 62 −10 10 64 67 −3 38 54 57 −3 3 56 57 −1 1 61 61 0 0 55 60 −5 5 9 49 42 7 7 50 43 7 7 55 496 6 52 52 0 0 10 48 44 4 4 51 46 5 5 72 60 12 12 51 46 5 5 11 71 65 6 673 68 5 5 75 76 −1 1 69 75 −6 6 12 48 50 −2 2 48 53 −5 5 49 54 −5 5 4749 −2 2 13 45 50 −5 5 46 51 −5 5 47 46 1 1 54 53 1 1 14 59 51 8 8 60 528 8 59 55 4 4 61 57 4 4 15 48 56 −8 8 50 55 −5 5 56 58 −2 2 49 55 −6 616 42 43 −1 1 44 43 1 1 43 42 1 1 46 37 9 9 17 54 56 −2 2 55 60 −5 5 6460 4 4 67 62 5 5 18 54 54 0 0 51 47 4 4 52 54 −2 2 59 53 6 6 19 42 43 −11 48 42 6 6 52 47 5 5 42 48 −6 6 26 49 46 3 3 49 48 1 1 42 41 1 1 44 422 2 27 60 53 7 7 52 54 −2 2 42 48 −6 6 46 46 0 0 Avg 51.3 50.7 0.53 51.951.5 0.33 55.5 54.5 1 53.5 53.2 0.33 51 51.7 55 53.4 White AnteriorLateral Deep Post Sup Posterior Pt R L Diff AV R L Diff AV R L Diff AV RL Diff AV 2 58 56 2 2 60 60 0 0 63 60 3 3 64 57 7 7 4 59 60 −1 1 60 57 33 58 61 −3 3 58 61 −3 3 5 54 51 3 3 51 48 3 3 55 51 4 4 55 52 3 3 6 5552 3 3 58 53 5 5 68 65 3 3 69 63 6 6 20 68 65 3 3 70 67 3 3 73 68 5 5 7471 3 3 21 62 61 1 1 61 55 6 6 68 67 1 1 68 70 −2 2 22 49 46 3 3 52 48 44 66 55 11 11 64 66 −2 2 23 67 62 5 5 70 65 5 5 88 81 7 7 77 70 7 7 2474 68 6 6 74 69 5 5 68 65 3 3 76 67 9 9 25 66 64 2 2 74 71 3 3 70 71 −11 71 66 5 5 Avg 61.2 58.5 2.7 2.9 63 59.3 3.7 3.7 67.7 64.4 3.3 4.1 67.664.3 3.3 4.7 59.9 61.2 66.1 66 Diff 8.85 9.45 11.1 12.6 Test 0.0000700.000091 0.000068 0.000005

Compartment Syndrome Patients Demographics Time Loca- p Pt Diast EarlyLate Fx tion Mech Injured Ht Wt BMI Side Sex Race Age 1 65 1 T/F P MVC 666 165 26.629 L M B 15 2 100 1 T/F M PvA 8 68 210 31.927 R M B 22 3 70 1T/F P GSW 5 73 170 22.426 L M B 19 4 76 1 T/F M PvA 10 71 165 23.01 R MB 59 5 89 1 P 6 MVC 4 74 220 28.243 L M B 59 6 55 1 P 6 MVC 10 69 21031.008 L M B 23 7 71 1 P 6 Fall 28 67 155 24.274 L M W 44 8 98 1 P 6Fall 6 68 200 30.407 L M H 32 9 58 1 T/F M MVC 13 66 150 24.208 L M A 62Avg 75.8 10 69.111 182.78 26.904 37.222 Std D 16.5 7.3314 2.9345 26.9393.6333 19.025

Initial Injury Study Non Compartment Syndrome Demographics Pt Mech Ht WtBMI Side Sex Race Age %O2 Time Injur Time p op Syst Diast Fx Open TschLocation 1 MVC 71 185 25.799 R M B 18 0 12 T/F 1 M 2 MVC 60 165 32.221 RF B 45 0 52 T/F 2 M 3 MVC 68 202 30.711 R F B 35 0 7 123 67 T/F 3A 3 M 4MVC 67 230 36.019 R M W 45 0 10 125 56 T/F 2 M 5 MVC 67 130 20.359 L M B18 0 31 134 79 T/F 1 M 6 Fall 72 205 27.8 R M W 60 0 15 120 69 SchVI 2 P7 Fall 69 161 23.773 L M B 26 0 16 129 76 Pilon 2 D 8 PvA 71 170 23.708R M W 31 0 11 141 59 T/F 1 M 9 Fall 67 215 33.67 L M B 45 0 18 151 95Pilon 2 D 10 Fall 66 195 31.47 R M B 30 0 5 117 58 Pilon 2 D 11 MVC 67140 21.925 R M B 52 0 48 T/F 3 P 12 MVC 72 210 28.478 L M B 55 0 9 183113 T/F 1 2 D 13 MVC 66 175 28.243 R F W 46 0 12 106 58 T/F 3A 2 M 14MVC 73 280 36.938 R M B 27 0 17 129 65 T/F 2 M 15 Fall 67 155 24.274 L MW 44 0 14 133 76 T/F 3 P 16 Fall 73 205 27.044 L M B 28 0 2 114 60 T/F 22 M 17 MVC 72 175 23.732 L M W 21 100 8 80 24 T/F 1 M 18 MVC 75 34543.117 R M W 42 0 14 131 85 SchV 2 P 19 MVC 68 175 26.606 R F B 42 0 9163 88 Pilon 2 1 D 20 MVC 70 190 27.259 R M W 22 0 21 153 93 Pilon 2 2 D21 PvA 70 170 24.39 R M B 54 100 32 140 75 T/F 3A 3 M 22 PvA 68 16825.542 L M B 38 0 2 131 78 T/F 3 M 23 Blow 71 195 27.194 L M H 29 0 19137 67 T/F 1 M 24 MVC 68 165 25.085 L M B 26 0 13 148 87 Sch V 2 P 25MVC 64 210 36.042 R F B 23 0 5 123 49 T/F 1 M 26 MVC 68 165 25.085 L M B26 0 13 148 87 Sch V 2 P Avg 68.8 191.58 28.326 10-L 5 8 35.692 2 15.962133 72.348 3-Plat 7  7-1's 5-P Med 15-R 20 17 17-T/F 13-2's 14-M Std D3.21 43.706 5.3403 12.315 12.389 20.596 18.527 5-pilon  5-3's 6-D pValNon Compartment Syndrome 2 Days Post-Op Demographics Pt Mech Ht Wt BMISide Sex Race Age Surgery Time injur Time p op Syst Diast Fx Open TschLocation 1 GSW 71 212 29.565 L M B 32 IMN 60 36 148 84 T/F 3 M 2 PvA 69175 25.84 R M H 34 IMN 130 119 116 65 T/F 3A 3 M 3 MVC 67 130 20.359 L MB 18 IMN 75 43 135 73 T/F 1 M 4 Fall 72 205 27.8 R M W 60 ExF 48 35 10157 SkVI 2 P 5 MVC 74 200 25.676 R M B 48 ORIF 96 45 148 103 F 2 1 D 6Fall 69 161 23.773 L M B 26 ORIF 133 40 134 77 Pilon 2 D 7 MVC 62 11521.031 L F W 22 ORIF 90 44 107 67 Pilon 1 D 8 PvA 75 170 21.246 R M B 47IMN 43 31 131 86 T/F 2 2 D 9 Fall 64 170 29.177 L F W 51 ExF 47 41 14479 Pilon 2 D 10 PvA 71 170 23.708 R M W 31 IMN 82 40 148 84 T/F 1 M 11MVC 66 175 28.243 R F W 46 IMN 60 42 112 61 T/F 3A 3 M 12 Fall 73 20527.044 L M B 28 IMN 42 32 135 71 T/F 2 3 M 13 MVC 68 175 26.606 R F B 42ExF 64 37 122 79 Pilon 1 D 14 PvA 70 170 24.39 R M B 54 ExF 56 33 119 55T/F 3A 3 M 15 MVC 70 190 27.259 R M W 22 ExF 58 46 105 68 T/F 2 3 D 16PvA 68 168 25.542 L M B 38 IMN 53 42 115 65 T/F 3 m 17 MVC 68 165 25.085L M B 26 ExF 87 27 137 85 Sch V 2 P Avg 69.2 173.88 25.432 36.765 7243.118 126.88 74.059 Med Std D 3.4 25.085 2.7582 12.612 27.868 20.28515.898 12.351 pVal

Uninjured Subjects (Normal NIRS Values) Demographics Time p Inj Pt Ht WtBMI Sex Race Age Injury wk Syst Diast 1 64 130 22.312 F B 18 none 108 672 72 175 23.732 M W 28 none 117 65 3 69 180 26.578 M B 33 fing Fx 10 13987 4 67 185 28.972 M W 36 none 124 78 5 60 110 21.481 F H 28 none 124 786 70 175 25.107 M W 32 none 125 71 7 66 200 32.277 M B 29 none 144 92 868 200 30.407 M B 32 none 125 65 9 68 188 28.582 M B 58 none 150 81 1069 192 28.35 M B 48 Clav fx 6 149 51 11 66 200 32.277 F B 58 none 143 8112 71 180 25.102 M B 28 none 125 85 13 66 142 22.917 F B 34 none 126 8914 62 196 35.845 F B 24 none 124 75 15 69 186 27.464 F B 42 none 132 9016 63 138 24.443 M B 39 none 119 70 17 57 132 28.561 F B 43 none 151 9118 71 175 24.405 M B 21 none 123 68 19 69 160 23.625 M B 21 none 133 7820 76 265 32.253 M W 26 none 144 87 21 67 160 25.057 M W 25 none 146 7022 63 117 20.723 F W 51 none 120 73 23 74 230 29.527 M W 32 none 123 6924 72 195 26.444 M W 33 none 118 77 25 72 205 27.8 M W 23 none 124 98Avg 67.6 176.64 26.97 33.68 8 130.24 77.44 T avg Std D 4.43 35.2223.7986 11.022 2.8284 12.011 10.863

White vs. Dark Pigmented Skin Comparison Demographics African American 164 130 22.312 F B 18 none 108 67 3 69 180 26.578 M B 33 fing 10 139 87Fx 7 66 200 32.277 M B 29 none 144 92 8 68 200 30.407 M B 32 none 125 659 68 188 28.582 M B 58 none 150 81 10 69 192 28.35 M B 48 Clav 6 149 51fx 11 66 200 32.277 F B 58 none 143 81 12 71 180 25.102 M B 28 none 12585 13 66 142 22.917 F B 34 none 126 89 14 62 196 35.845 F B 24 none 12475 15 69 186 27.464 F B 42 none 132 90 16 63 138 24.443 M B 39 none 11970 17 57 132 28.561 F B 43 none 151 91 18 71 175 24.405 M B 21 none 12368 19 69 160 23.625 M B 21 none 133 78 5 69 150 22.149 M H 24 ROH 2 12080 arm 8 63 98 17.358 F B 25 MC fx 2 120 81 Avg 66.5 173.27 27.543132.73 78 White 2 72 175 23.732 M W 28 none 117 65 4 67 185 28.972 M W36 none 124 78 5 60 110 21.481 F H 28 none 124 78 6 70 175 25.107 M W 32none 125 71 20 76 265 32.253 M W 26 none 144 87 21 67 160 25.057 M W 25none 146 70 22 63 117 20.723 F W 51 none 120 73 23 74 230 29.527 M W 32none 123 69 24 72 195 26.444 M W 33 none 118 77 25 72 205 27.8 M W 23none 124 98 Avg 69.3 181.7 26.11 126.5 76.6 Diff Test

APPENDIX B Tourniquet Study Data INVOS Diff Perfusion from BaselineSubject INVOS pressure (PP) 1 67 71 0 69 65 2 63 56 −4 62 36 −5 61 26 −659 17 −8 56 5 −11 55 −1 −12 31 −11 −36 16 −21 −51 15 −35 −52 2 65 88 066 75 1 64 63 −1 63 58 −2 57 48 −8 58 43 −7 60 35 −5 60 15 −5 58 4 −7 53−13 −12 28 0 −37 20 −34 −45 3 63 74 0 66 59 3 67 49 4 65 42 2 66 27 3 6515 2 64 10 1 61 2 −2 58 −11 −5 52 −6 −11 33 −28 −30 20 −34 −43 4 72 71 079 60 7 74 48 2 71 41 −1 71 32 −1 73 21 1 71 20 −1 70 5 −2 68 −9 −4 65−13 −7 63 −26 −9 47 −32 −25 39 −46 −33 5 69 86 0 70 73 1 72 59 3 69 55 069 43 0 66 32 −3 66 20 −3 64 13 −5 62 −1 −7 59 −7 −10 35 −20 −34 22 −31−47 6 58 72 0 60 59 2 58 49 0 61 39 3 58 27 0 58 19 0 57 6 −1 53 −4 −548 −14 −10 23 −25 −35 15 −31 −43 7 67 73 0 68 64 1 68 64 1 68 44 1 68 281 66 27 −1 65 9 −2 63 4 −4 61 −7 −6 46 −18 −21 15 −25 −52 8 65 54 0 6540 0 64 26 −1 63 15 −2 62 4 −3 59 1 −6 41 −10 −24 24 −19 −41 16 −26 −499 68 67 0 71 59 3 70 47 2 67 41 −1 65 27 −3 64 19 −4 64 10 −4 63 −4 −561 −8 −7 51 −18 −17 24 −23 −44 15 −40 −53 10 69 69 0 66 57 −3 62 46 −764 39 −5 64 27 −5 63 17 −6 61 5 −8 62 −1 −7 57 −13 −12 53 −23 −16 39 −33−30 33 −38 −36 11 62 67 0 60 55 −2 60 45 −2 58 33 −4 58 29 −4 53 15 −952 4 −10 43 −5 −19 20 −12 −42 15 −21 −47 12 71 66 0 69 57 −2 68 49 −3 6442 −7 65 29 −6 62 28 −9 61 12 −10 58 −1 −13 50 −9 −21 40 −17 −31 28 −26−43 24 −37 −47 13 67 69 0 69 59 2 67 48 0 68 41 1 65 28 −2 64 21 −3 63 8−4 63 5 −4 57 −9 −10 50 −21 −17 23 −26 −44 15 −37 −52 14 67 68 0 68 53 165 45 −2 64 35 −3 63 21 −4 63 16 −4 61 5 −6 59 −3 −8 54 −13 −13 40 −23−27 34 −35 −33 33 −38 −34 15 70 52 0 70 43 0 70 29 0 69 19 −1 68 10 −265 2 −5 59 −10 −11 42 −16 −28 36 −27 −34 34 −35 −36 33 −35 −37 16 72 770 71 63 −1 68 49 −4 68 45 −4 66 27 −6 66 24 −6 63 9 −9 60 −3 −12 53 −7−19 45 −25 −27 40 −28 −32 38 −34 −34 17 61 76 0 59 66 −2 58 59 −3 61 500 59 37 −2 58 29 −3 58 19 −3 59 12 −2 55 10 −6 45 −9 −16 24 −19 −37 1874 69 0 74 61 0 73 48 −1 73 39 −1 73 28 −1 71 17 −3 69 12 −5 67 3 −7 64−7 −10 45 −21 −29 39 −28 −35 36 −37 −38 19 72 67 0 73 54 1 74 45 2 74 372 73 29 1 71 16 −1 69 7 −3 67 −3 −5 66 −15 −6 60 −21 −12 52 −33 −20 49−43 −23 48 −44 −24 20 70 78 0 70 70 0 70 54 0 69 45 −1 68 28 −2 66 24 −462 16 −8 60 3 −10 59 −8 −11 53 2 −17 32 −16 −38 25 −35 −45

What is claimed is:
 1. A computer-implemented method for automaticallymonitoring oxygenation levels of a compartment of injured tissue of ahuman body for automatically detecting conditions of a compartmentsyndrome, comprising: automatically monitoring oxygenation levels of thecompartment of injured tissue in a continuous manner with a firstnon-invasive sensor; automatically monitoring oxygenation levels ofhealthy tissue in a continuous manner with a second non-invasive sensor,the second non-invasive sensor detecting systemic perfusion of the humanbody from the healthy tissue; automatically monitoring blood pressure ofthe human body in a continuous manner with a non-invasive blood pressuredevice, the blood pressure comprising diastolic and systolic bloodpressure values; and automatically activating an alarm with a computingdevice when both the blood pressure of the human body comprising thediastolic and systolic blood pressure values decreases and oxygenationlevels of the first non-invasive sensor for the compartment startdecreasing in value compared to the oxygenation levels of the secondnon-invasive sensor for the healthy tissue, the second non-invasivesensor providing a basis for comparison for relative oxygenation levelsof injured tissue.
 2. The method of claim 1, further comprisingdisplaying oxygenation levels of the compartment on a display device. 3.The method of claim 1, further comprising providing an alignmentmechanism on the first non-invasive sensor.
 4. The method of claim 1,further comprising calculating, with the computing device, a runningaverage for the blood pressure and oxygenation levels.
 5. The method ofclaim 1, wherein activating an alarm with the computing device furthercomprises activating an alarm that produces one or more alerts on adisplay device.
 6. The method of claim 1, further comprisingcalculating, with the computing device, a mean arterial pressure (MAP)and displaying the mean arterial pressure (MAP) on a display device. 7.A system for automatically monitoring oxygenation levels of acompartment of a human body for automatically detecting conditions of acompartment syndrome, the system comprising: a plurality of non-invasivesensors for automatically detecting oxygenation levels of the human bodyin a continuous manner; a non-invasive blood pressure device forautomatically sensing blood pressure of the human body in a continuousmanner, the blood pressure comprising diastolic and systolic bloodpressure values; and a computing device coupled to the non-invasivesensors and non-invasive blood pressure device, wherein the computingdevice is configured for: monitoring oxygenation levels of injuredtissue of a compartment from a first non-invasive sensor of theplurality of non-invasive sensors; monitoring oxygenation levels ofhealthy tissue from a second non-invasive sensor of the plurality ofnon-invasive sensors; monitoring the blood pressure of the human body;and automatically activating an alarm when both the blood pressurecomprising the diastolic and systolic blood pressure values of the humanbody decreases and oxygenation levels of the first non-invasive sensorstart decreasing in value compared to the oxygenation levels of thesecond non-invasive sensor, the second non-invasive sensor providing abasis for comparison for relative oxygenation levels of injured tissue.8. The system of claim 7, wherein the computing device is furtherconfigured for increasing a frequency at which the oxygenation levelsand blood pressure are monitored when the oxygenation levels and bloodpressure fall within a predetermined range of values.
 9. The system ofclaim 7, further comprising a display device configured forsimultaneously displaying the oxygenation levels and diastolic andsystolic blood pressure values of the human body.
 10. The system ofclaim 9, wherein one or more of the first non-invasive sensor and thesecond non-invasive sensor each comprises an array of non-invasivesensing elements.
 11. The system of claim 10, wherein the computingdevice is further configured for controlling a timing for activatingrespective non-invasive sensors of the array in order to provide scansof different portions of the human body.
 12. The system of claim 11,wherein the computing device is further configured for calculating arunning average for the blood pressure and oxygenation levels.
 13. Thesystem of claim 12, wherein the alarm comprises at least one of anaudible alarm and visual alarm.
 14. The system of claim 13, wherein thecomputing device is further configured for calculating a mean arterialpressure (MAP) that is displayed on the display device.
 15. A system forautomatically monitoring oxygenation levels of a compartment of a humanbody for automatically detecting conditions of a compartment syndrome,the system comprising: a plurality of non-invasive sensors forautomatically detecting oxygenation levels of the human body in acontinuous manner; a non-invasive blood pressure device forautomatically sensing blood pressure of the human body in a continuousmanner, the blood pressure comprising diastolic and systolic bloodpressure values; and a computing device coupled to the non-invasivesensors and non-invasive blood pressure device, wherein the computingdevice is configured for: monitoring oxygenation levels of an injuredportion of the human body from a first non-invasive sensor of theplurality of non-invasive sensors; monitoring oxygenation levels of anuninjured portion of the human body from a second non-invasive sensor ofthe plurality of non-invasive sensors; monitoring the blood pressure ofthe human body; comparing oxygenation levels between the injured portionof the human body and the uninjured portion of the human body; andautomatically activating at least one of an audible alarm and visualalarm when both the blood pressure comprising the diastolic and systolicblood pressure values of the human body decreases and when theoxygenation levels of the first non-invasive sensor start decreasingcompared to the oxygenation levels of the second non-invasive sensor,the second non-invasive sensor providing a basis for comparison forrelative oxygenation levels of injured tissue.
 16. The system of claim15, further comprising a display device configured for simultaneouslydisplaying the oxygenation levels and diastolic and systolic bloodpressure values of the human body.
 17. The system of claim 15, whereinthe computing device is further configured for activating an alarm whenthe blood pressure and oxygenation levels approach predefined levels.18. The system of claim 17, wherein the computing device is furtherconfigured for controlling a timing for activating respectivenon-invasive sensors in order to provide scans of different portions ofthe human body.
 19. The system of claim 18, wherein the computing deviceis further configured for calculating a running average for the bloodpressure and oxygenation levels.